Ross Kemp's mind went blank after he inhaled a small amount of the drug known as 'spice' when filming a documentary inside a British prison.
The documentary maker and former Eastenders actor was unable to speak after he breathed in the residue of a small amount of the popular prison and street drug left inside the bottom of an inmate's vapouriser.
Speaking to the Sun, Ross said: "I am rarely lost for words but as I turn to camera, I have lost the ability to speak.
"My brain has gone blank, my hands are clammy and my mouth is dry."
The variety of spice Ross tried is known as 'Man Down', said to be one of the strongest strains of the now illegal former legal-high. Ross said Man Down "does exactly what it says on the tin".
The 55-year-old Londoner was visiting Belmarsh Prison to film a two part documentary, Welcome To HMP Belmarsh With Ross Kemp, which debuts on ITV on Thursday/
The south-east London prison has held the likes of Ian Huntley, rapist John Worboys and Lee Rigby's killers. It was home to 187 murderers and 17 terrorists when ITV was filming there.
The inmates Ross met included far-right campaigner Stephen Yaxley-Lennon, more commonly known as Tommy Robinson.
Welcome To HMP Belmarsh With Ross Kemp starts on Thursday, January 9, on ITV at 9pm.
