Dame Joan Collins mistakenly thought Martin Compston was threatening to kill her after he objected to Rangers anthem Simply The Best being played at an awards ceremony.
The Celtic-daft Line of Duty star refused to stand up to applaud and made a throat cutting gesture when the Tina Turner hit was belted out as the actress walked on stage at the National Television Awards.
The clip went viral and many viewers and the Dynasty star herself were left bemused at the actor's reaction.
TV presenter Piers Morgan told how he had to explain to the 88-year-old that the Scottish actor was unhappy at the song choice because of his football allegiances and had no ill will towards her.
Writing in his Mail On Sunday column, he said: "At the end of the dreary show, Dame Joan Collins glided out like a ray of glittering Hollywood sunshine shining out over a sea of dull reality TV plankton, prompting the whole crowd to give her a roaring standing ovation as Tina Turner's Simply The Best belted out.
"Well, all except one person. Sitting firmly unimpressed in his front row seat was Line Of Duty star Martin Compston, who instead looked furious and performed a sinister throat-cutting sign with his hand.
"The clip soon went viral on Twitter with people aghast at his oddly hostile behaviour towards a beloved national treasure.
"I found it equally baffling; Compston was in my World XI when I was a manager at Soccer Aid several years and you won't meet a nicer bloke."
Morgan, 56, discovered the real reason behind 37-year-old Compston's snub before having dinner with Collins the next day.
He said: "Mystery solved: Compston's throat slashing manoeuvre was because he's a diehard Celtic fan and Simply The Best is the adopted anthem for their bitter rivals Rangers.
"So, this had nothing to do with Dame Joan, but that might not cut any ice with the great lady who isn't known for suffering either fools or perceived slights.
"'Enjoy the NTAs?' I asked her soon after we sat down at Cambio de Tercio in Chelsea with our other halves.
"'Well, the standing ovation was a wonderful surprise!' she exclaimed. 'But then I looked down and saw this Line Of Duty actor sitting there scowling and cutting his hand across his throat and couldn't understand why he wanted to kill me!'
"I burst out laughing. 'He doesn't actually want to kill you '
"'That's a relief,' Joan chuckled. 'What does he want?' I explained the Celtic/Rangers backdrop, sparing Compston a lifetime of Alexis Carrington-style vengeful wrath."
Morgan told how he got in touch with Compston to tell him he had cleared the air between him and Collins.
Writing in his column, he added: "In the cab home, I messaged him: 'Had dinner with Dame Joan and had to reassure her that you don't want to cut her throat.'
"'Haha, thanks big man!' he replied. 'I just meant cut the music - there's not a chance I can stand for that song. But having Joan Collins think I want to kill her was not something I thought would happen at the outset of my career. I owe you a beer '."
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