Ashton Kutcher has tense first day on set of US sitcom

The 33-year-old Hollywood star – who replaced troubled actor Charlie Sheen on the hit CBS show – first appeared on set on Monday, but the atmosphere was reportedly so strained that onlookers could “cut the air with a knife”.

CBS programming chief Nina Tassler reportedly told Fox News: 'When everybody walked on the set, you could cut the air with a knife.'

However, the tension was quickly broken by Two And A Half Men star Jon Cryer – who plays Charlie's on-screen brother Alan Harper – who gave a “touching” speech to the cast and crew.

Tassler added: 'He [Cryer] gave a little speech. I can't even remember the words. It was just something very touching.

'Then, when you hear that first actor mutter that first line, you breathe a sigh of relief.'

Kutcher will make his debut in the season premiere on 19 September as Walden Schmidt, an internet billionaire with a broken heart.