The paparazzi are camped outside their house and their marriage has been headline news for days, but for Gordon and Tana Ramsay it's business – and cooking – as usual.

In his first public appearance since allegations of his infidelity surfaced the TV chef joked his way through a live cookery demo at the NEC in Birmingham, as his wife smiled and chatted with fans at her own cookbook signing just yards away.

The father of four bounded on to the stage and told the audience, which included his mother: "What a week I've had. My mum is in here tonight so I'm on my best behaviour. I didn't do it Mum. I love you."

Referring to a trick he played on cookery queen Delia Smith when he attended one of her book signings in disguise Gordon said: "I got up close and personal with Delia - I got in there."

"I have been following her for 25 years and wanted my book signed. But I didn't have the guts to ask her for a kiss," he added.

Joking about Delia's latest tome How To Cheat he said: "She gave me a book on how to cheat. All I wanted to do was show her my recipes for spotted dick."

The celebrity restaurateur also suggested the arrival of a new mattress at the Ramsay home had fuelled media interest in him.

"Everyone probably thought it was because I had to sleep in the basement," he quipped, before adding in his usual colourful language: "matress, mistress, matress, what a load of b*******."

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