Former Home Secretary and Hull MP revealed as Pharaoh on ITV's The Masked Singer
Mr Johnson's identity was revealed after he failed to impress the panel of judges with his rendition of Walk Like An Egyptian by The Bangles, and progress through to the next round.
The Labour politician, who served as an MP for Hull West and Hessle for 20 years until his retirement in 2017, said he had felt like "a spaceman" wearing the elaborate Egyptian-inspired outfit.
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Hide AdThe ITV programme, which debuted on Saturday and continued on Sunday night, sees celebrities and public figures compete dressed in elaborate outfits which conceal their identity.
Mr Johnson said it had been "very hard" to keep his role a secret.
He added: "The show is so extraordinary it's almost perverse to keep mute about it."
Speaking after he was unmasked by host Joel Dommett, Mr Johnson said: "It was brilliant. What a show. In the mask you feel like a bit of a spaceman. You are removed from it all.
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Hide AdExtra £2m put into fund to help Yorkshire farmers recover from floodingFinal chance to save United Kingdom from Brexit break-up, warns Labour MP and mayor Dan Jarvis"I couldn't really see the dancers dancing around me. It was so much fun. A bit of karaoke as well."
The judging panel of Jonathan Ross, Davina McCall, Ken Jeong and Rita Ora failed to guess his identity despite a number of clues.
"I saw the queen everyday" pointed towards his former job as a postman, and "my place of work is also a piece of furniture" hinted towards his governmental role in the Cabinet.
Before he was unmasked, Ross suggested Pharoah might be Brexit Party politician Ann Widdecombe, who has appeared on Strictly Come Dancing.
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Hide AdAnd at one point Ross even mentioned Mr Johnson's name, before conversation swiftly moved on.
Brexit must not put United Kingdom at risk – Dan Jarvis'It's time to bring our girl home' - Bradford West MP Naz Shah on Government's 'shame' over Ayia Napa gang rape caseMr Johnson said of the judging panel: "They were full of energy and humour but I wondered how they could have even suspected that Pharaoh was Ann Widdecombe."
It comes after the debut episode of the surreal celebrity guessing game won Saturday night's ratings battle against BBC One's The Greatest Dancer, pulling in over two million more viewers.
The Masked Singer kicked off with an average audience of 5.5 million when it aired at 7pm, according to overnight ratings.
The Greatest Dancer, which also aired at 7pm, had an average of 3.2 million viewers.
The Masked Singer continues on Saturday at 7pm on ITV.