Boris Johnson tested positive for Covid-19 on March 26. The Prime Minister had mild symptoms and was advised by the Chief Medical Officer to get a test.
Then, on April 5, he spent the night in an NHS hospital after being admitted with persistent coronavirus symptoms. His doctor insisted that the admission was precautionary.
But Downing Street announced on April 6 that he had been moved to intensive care after his coronavirus symptoms worsened.
He has been given oxygen after suffering breathing difficulties but he has not been placed on a ventilator.
Mr Johnson was on Wednesday night spending his third night in intensive care at St Thomas’ Hospital in central London, No 10 said, adding that he “continues to make steady progress”.
Rishi Sunak, the Chancellor of the Exchequer, told a 10 Downing Street press briefing that Mr Johnson “has been sitting up in bed and engaging positively with the clinical team”.
What happened before the PM went to hospital?
UK Health Secretary Hancock also confirmed he tested positive for Covid-19 following the Prime Minister's announcement. Dominic Cummings, the Prime Minister's Chief Adviser, is self-isolating after presenting symptoms.
Mr Johnson has been self-isolating in 11 Downing Street which has been sealed off, effectively "making it a house", says the Prime Minister's official spokesman.
The Prime Minister's meals were being left at doors between 10 and 11 Downing Street.
Mr Johnson had been continuing to lead the Government's handling of the crisis by videophone because he had been feeling well enough to continue to work.
Mr Johnson, 55, announced the test results by posting a video on Twitter on March 27, where he said he had developed a temperature and a persistent cough.
He used the opportunity to thank the NHS and said that it was "very moving" to participate in the clap for NHS staff on March 26. He went on to thank the national services for their "great national effort" as well as thanking those who have signed up to volunteer.
He said on March 27: "Over the last 24 hours I have developed mild symptoms and tested positive for coronavirus.
"I am now self-isolating, but I will continue to lead the Government’s response via video-conference as we fight this virus.
"Together we will beat this."
A Downing Street spokesman said: "After experiencing mild symptoms yesterday, the Prime Minister was tested for coronavirus on the personal advice of England's Chief Medical Officer, Professor Chris Whitty.
"The test was carried out in No 10 by NHS staff and the result of the test was positive. In keeping with the guidance, the Prime Minister is self-isolating in Downing Street."
On April 2, it was reported that Mr Johnson was still showing signs of coronavirus and may have to continue self-isolating.
Three days later, the Prime Minister was admitted to hospital because his symptoms had not passed.
Number 10 said that he was taken to hospital by private car for tests after he continued to report a high temperature. Aides insisted that he remained in charge of the Government.
On April 6, however, Downing Street announced that the Prime Minister had been transferred to intensive care after his symptoms worsened. He was understood to have been moved to the ICU at about 7pm as a precaution should he require ventilation to aid his recovery.
Has anyone stepped in for Mr Johnson as Deputy Prime Minister?
Foreign Secretary Dominic Raab had been advised by Boris Johnson to deputise him "where necessary" after the Prime Minister's hospitalisation.
After Mr Johnson was admitted to intensive care, it was confirmed that Mr Raab will lead the UK's response to the coronavirus crisis.
Mr Raab will lead Cobra meetings while the Prime Minister is in hospital.
Rishi Sunak has been named as Boris Johnson's second "designated successor" amid claims that Michael Gove was overlooked due to question marks over his loyalty.
Read more about who might step in for Mr Johnson here.
Who did the Prime Minister come into close contact with?
UK Health Secretary Hancock confirmed he tested positive for Covid-19 following the Prime Minister's announcement.
In a tweet Mr Hancock said: "Following medical advice, I was advised to test for coronavirus.
"I've tested positive.
"Thankfully my symptoms are mild and I’m working from home and self-isolating."
He went on to add that it was "vital we follow the advice to protect our NHS and save lives".
The Prime Minister has regular audiences with the Queen. Asked about the wellbeing of the Queen, following the Prime Minister's diagnosis, a spokesman for Buckingham Palace said: "Her Majesty the Queen remains in good health. The Queen last saw the Prime Minister on the 11th March and is following all the appropriate advice with regards to her welfare."
The Queen, 93, and Duke of Edinburgh, 98, are practising “social distancing” in Windsor, in line with government advice for the over-70s.
She is relying on modern technology to stay in touch with her grandchildren and great-grandchildren during a period of social distancing.
The Queen and Mr Johnson had their weekly audience via telephone call last Wednesday.
Multiple Downing Street staff are also believed to be in self-isolation. The PM recently held Cabinet by video conference, and talked to the G20 leaders on a virtual meeting on Thursday, as pictured below.
Rishi Sunak, the Chancellor of the Exchequer, who was last seen observing the two-metre rule while clapping for the NHS alongside the Prime Minister, has not taken a test and is not displaying symptoms.
Mr Sunak is now working from his office in HM Treasury on Whitehall. It is understood that the Chancellor has not yet moved his family into the flat that he is entitled to above 10 Downing Street.
The Prime Minister's pregnant partner Carrie Symonds is isolating alone away from No 10 with the couple's dog, Dilyn.
She later revealed she had "spent the past week in bed" after suffering coronavirus symptoms but is now recovering.
The 32-year-old, who is expecting the couple's baby in early summer, falls into the group of vulnerable people urged to avoid contact with those with symptoms of Covid-19.
No 10 have said that they would not be pursuing contact tracing. Instead, people who had symptoms would be required to self-isolate.
Politicians wish the Prime Minister well on social media
A number of politicians wished the Prime Minister a full recovery on Twitter.
New Labour leader Sir Keir Starmer said: "Terribly sad news. All the country’s thoughts are with the Prime Minister and his family during this incredibly difficult time."
Former Labour leader Jeremy Corbyn led messages from across the political divide.
He tweeted: "I wish the Prime Minister a speedy recovery and hope his family are safe and healthy. Coronavirus can, and does, affect anyone. Everyone be safe. Our own health depends on everybody else."
Shadow home secretary Diane Abbott tweeted: "I don't wish anyone ill. I wish the Prime Minister a speedy recovery. I hope everyone in coming days gets the care and medical attention they need."
The Mayor of London, Sadiq Khan, posted: "Sorry to hear this and hope you feel better soon.
"Thank you for everything your Government is doing to help us fight this.
"This is a reminder that anyone can get Covid-19. We must all follow the rules and stay at home to support our amazing NHS staff to save lives."
Nigel Farage posted: "Wishing @BorisJohnson well and a very rapid recovery."
And former chancellor Sajid Javid replied: "Get well soon. Sending you best wishes from Javid family and Bailey."
Donald Trump said: "I also want to send best wishes to a very good friend of mine, and a friend to our nation, prime minister Boris Johnson. "We're very saddened to hear he was taken into intensive care this afternoon, a little while ago. "And Americans are all praying for his recovery. He's been a really good friend, he's been really something very special. Strong, resolute, doesn't quit, doesn't give up."
European Council President Charles Michel tweeted: "Get well soon @BorisJohnson Europe wishes you a speedy recovery. I believe we'll win this fight against Covid-19 together."
Read how the world reacted after Mr Johnson was moved to the intensive care unit.
Timeline of every public appearance by the Prime Minister in the month before he was diagnosed
By the Telegraph’s Christopher Hope
Friday, February 28
Boris Johnson visits Kettering General Hospital's A&E department, posing for selfies with patients.
Tuesday, March 3
5pm: Boris Johnson hosts press conference alongside chief medical officer Sir Patrick Vallance at 10 Downing Street days after a visit to Kettering hospital. He says: "I was at a hospital the other night where there were a few coronavirus patients. I shook hands with everybody you will be pleased to know and I continue to shake hands."
Number 10 sources later said he had not shaken hands with any coronavirus patients at the hospital.
Wednesday, March 4
Boris Johnson faces Jeremy Corbyn at Prime Minister's Questions. The PM tells MPs that workers will not have to wait three days to receive statutory sick pay.
Monday, March 9
3pm: Boris Johnson, with his pregnant fiancee Carrie Symonds on his arm, meets the Queen, the Prince of Wales and other members of the Royal Family for the annual Commonwealth Day service at Westminster Abbey.
5pm: Boris Johnson hosts a press conference at 10 Downing Street alongside Sir Patrick Vallance and UK chief medical adviser, Professor Chris Whitty, saying that containment of the virus is now "extremely unlikely to work on its own".
Wednesday, March 11
Boris Johnson chairs his weekly meeting of the Cabinet in 10 Downing Street, a day later than usual.
Boris Johnson faces Jeremy Corbyn at Prime Minister's Questions in the Commons and sits alongside Rishi Sunak as the Chancellor unveils £30 billion worth of measures to tackle coronavirus in the Budget.
Afternoon: Mr Johnson meets the Queen for her weekly audience with him – the last time they meet in person.
Thursday, March 12
5pm: Boris Johnson hosts a 10 Downing Street press conference alongside Patrick Vallance and Professor Chris Whitty, saying that Britain was facing the “worst public health crisis for a generation”.
Monday, March 16
5pm Boris Johnson hosts a press conference at 10 Downing Street with Professor Chris Whitty and Sir Patrick Vallance, saying: "Now is the time for everyone to stop non-essential contact with others and to stop all unnecessary travel."
Tuesday, March 17
Boris Johnson chairs his weekly Cabinet meeting.
5pm: The Prime Minister, with Rishi Sunak alongside him, unveils £330 billion-worth of loans for businesses affected by coronavirus.
Wednesday, March 18
Boris Johnson faces Jeremy Corbyn at Prime Minister's Questions in the House of Commons.
5pm: Boris Johnson hosts a press conference at 10 Downing Street announcing that all schools in England will close for most pupils from Friday, March 20.
Thursday, March 19
5pm: Boris Johnson hosts a press conference at 10 Downing Street, flanked by Professor Chris Whitty, and Sir Patrick Vallance. The Prime Minister says the UK can "turn the tide" on the coronavirus crisis within 12 weeks.
Friday, March 20
5pm: Boris Johnson hosts a press conference at 10 Downing Street and announces that cafes, pubs and restaurants must close from Friday night – except for take-away food – to tackle coronavirus.
Sunday, March 22
4.30pm: Boris Johnson hosts a press conference at 10 Downing Street, accompanied by Robert Jenrick, the Communities Secretary, and Dr Jenny Harries, the Deputy Chief Medical Officer, announcing that 1.5 million vulnerable people must be "shielded" at home from coronavirus.
Tuesday, March 24
9.30am: The Prime Minister chairs his weekly Cabinet meeting. Most Cabinet ministers attend by video conference. Only Health secretary Matt Hancock, Cabinet secretary Sir Mark Sedwill and Professor Chris Whitty are with him in the Cabinet room.
Wednesday, March 25
Boris Johnson faces Jeremy Corbyn at Prime Minister's Questions in the Commons for the last time before Parliament breaks for the Easter recess.
5pm: Boris Johnson hosts a press conference at 10 Downing Street flanked by Professor Chris Whitty, and Sir Patrick Vallance, The PM says that "in just 24 hours 405,000 people have responded to the call" to assist the NHS.
Thursday, March 26
Early afternoon: Boris Johnson complains of a cough and mild temperature.
Late afternoon: Boris Johnson is tested for coronavirus.
8pm: Boris Johnson joins Chancellor Rishi Sunak to clap for NHS workers in Downing Street.
Midnight: Results come back to show the Prime Minister has tested positive for Covid-19.
Friday, March 27
9.30am: Boris Johnson chairs meeting of coronavirus war cabinet via video link.
10.30am: Boris Johnson records video titled "update from me" on Facebook in which he says he has "mild symptoms" of coronavirus but adding: "I am now self-isolating, but I will continue to lead the government’s response via video-conference as we fight this virus."