The Royal Navy launched a top-level inquiry into the running of one its most secretive bases after claims of rape and sexual misconduct by British sailors.

The Sunday People has learned a US Navy sailor was allegedly raped, a second US servicewoman was sexually assaulted and a third sexually harassed by Royal Navy personnel.

But a probe into the base, on Diego Garcia in the Indian Ocean, was only launched by Navy chief Admiral Tony Radakin after a whistleblower wrote to him alleging leadership failures.

The 10-week inquiry, concluded last month, also unearthed claims of sexual assault, racist bullying, harassment and discrimination against women.

In the letter, Marine John Lewis wrote of a series of incidents between July 2019 and January 2020 he felt would harm the Navy’s reputation.

Marine Lewis, 36, also claimed he was victimised after defending a young US sailor when she told him she had been sexually harassed by a drunk, British sailor more than twice her age.

He explained he had “personally intervened, preventing a potentially embarrassing international incident”.

Stock image of woman in silhouette
There have been a number of serious allegations (stock image)

Marine Lewis wrote: “My moral courage as a father was outraged, hence my intervention.”

The commando, who served in Iraq, punched the British sailor once and was charged with ABH and sent home.

Four months later – in January 2020 – the sailor involved in the incident was charged with another sexual assault.

Marine Lewis wrote that while he himself was cleared unanimously by a court martial his defence had cost more than £15,000 leaving him “struggling to support my young family”.

The case also damaged his career and caused him “ongoing” mental health issues, he claimed.

Marine Lewis wrote: “No concern was given for my welfare at any point.

“I was treated as guilty and not provided any direction, care or guidance from the chain of command.”

In the letter, seen by the Sunday People, Marine Lewis added: “I know of three incidents of a sexual nature whilst I was on the island.

"One leading hand offended twice and another once.

“This behaviour falls well short of what the Commandant General Royal Marines and Corps’ RSM would expect, surely a discharge and custodial sentence for the offenders is warranted.”

In the alleged rape of a US sailor, in 2019, the Navy defendant is to face a court-martial.

The Sunday People recently highlighted the issue of sexual abuse and rape in the forces. Hundreds of serving and former female personnel claim they were victims.

The Ministry of Defence has yet to release the findings of its inquiry into Diego Garcia, which is the largest island in the British Indian Ocean Territory, over 700 miles south of the Maldives.

A spokesperson said: “These matters are the subject of ongoing investigation and it would be inappropriate to comment any further at this time.”

The base there, known as the Naval Support Facility, is leased to the US military which uses it as a staging post for operations in the Middle East.