The 36-year-old has starred as DS Steve Arnott for all six series of the BBC thriller, which has now been running for a decade.
In that time it’s become one of the most heavily-guarded shows imaginable, with storyline twists being protected with AC-12 precision.
But back in series three Martin dropped the mother of all spoilers when he let slip Keeley Hawes’ return as Lindsay Denton – an hour before the episode aired.
The Scottish-born actor joins Jamie and Harry Redknapp, comedian Tom Davis and Daisy May Cooper on tonight’s Redknapp’s Big Night Out where he recalled the slip-up.
‘I was living in LA at the time and I think it was when Keeley Hawes came back so I put out ”she’s back everybody” but I forgot the clocks went forward in the UK so I put it out at 8 and the show came on at 9,’ he said.
‘Luckily everyone was going “what the f**k are you on about?” From that moment I’ve got the fear big time.’
This weekend Line of Duty series six concludes with a ‘chaotic’ finale, with the trailer confirming mysteries which have unraveled since the beginning of the show being wrapped up.
On the Shrine of Duty podcast, Martin hinted the upcoming episode could be the very last one. Sadly, on Redknapp’s Big night Out, he only doubled down.
‘If we do come back, which I genuinely know if we do it will always be one at a time because it builds the suspense,’ he said.
Understandably hacked off by the remark, King Gary star Tom bellowed: ‘Hold the f**k up – I thought there was a series seven?’
Martin coyly replied: ‘This might be the last one – you need to enjoy it.’
All will be revealed when Line of Duty airs this Sunday at 9pm on BBC One.
Redknapp’s Big Night Out continues tonight at 10pm on Sky One and TV streaming service NOW.
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