Sailors are set to be allowed to puff e-cigarettes in their nuclear submarines.
The move follows a fugitive whistleblower claiming unauthorised vaping was a safety risk.
Royal Navy medical officers now think there is no risk – and e-cigs would help ratings to give up real cigarettes, reports the Sunday People.
Weapons engineer William McNeilly, 25, went on the run after publishing an online dossier of alleged safety failings in the four-sub Trident fleet.
They included inadequate tests to see if missiles could be launched safely, alarm systems being muted because they kept going off and top secret documents being left unguarded.
McNeilly, who served aboard sub HMS Victorious, handed himself in and has now returned to duty.
Defence Secretary Michael Fallon dismissed his concerns as wrong or the result of misunderstandings.
Armed Forces Minister Penny Mordaunt said: “Only one of his allegations remains to be concluded – that electronic cigarettes were used on the submarine.”