The 'mind the gap' voice at Embankment station is different to all the other voices across the London Tube network - and there's a poignant reason why.
It all started just before Christmas seven years ago, when a very upset woman approached the staff at Embankment. She kept desperately asking why the voice had gone.
It took them a while to realise what she meant by 'the voice' - she meant the man who said 'Mind the Gap' in a booming, over-enunciating voice.
The staff explained that the system had been updated and new voices had been used, to which the woman said: "That voice was my husband."
The woman, a GP called Dr Margaret McCollum, told the staff how her husband was an actor, Oswald Laurence, and while he'd never been a huge success he had been the man who recorded all the announcements for the Northern Line in the 70s.
Oswald had died in 2007, leaving his widow heartbroken, but there was one thing that helped ease her pain - she could hear his voice every day on the way to work, and would sometimes sit on the platform to listen for a bit longer.
The staff felt awful for the woman, but they didn't know what to do as the whole system had been redone. They promised to look into it and see if the old recordings still existed.
In the new year Margaret was on her way to work when over the speakers she heard a familiar voice - it was her husband.
It turned out there were a lot of people at the station and across Transport for London who had lost loved ones and would give anything to hear their voice again, and they knew they had the power to give that to someone.
Archives were searched, old tapes found and restored, the code of the announcement system was altered and paperwork was filed.
Eventually they made Oswald talk again - both on a CD for Margaret and over the Tube loudspeaker.
So the next time you're at Embankment station take a moment to enjoy Oswald’s voice and appreciate how much joy a small, simple act of kindness can bring to people.
It was the perfect Christmas gift.