The boyband singer, 41, and the TV favourite, 43, have been on a string of intimate dates.

The lovebirds met when SHE played HIM in spoof boyband Fake That.

Redhead Catherine — famed for her gobby "Am I bovvered?" schoolgirl Lauren Cooper in her TV sketch show — took the part of Jason for Comic Relief in March.

She was joined by David Walliams as Howard Donald, Alan Carr as Mark Owen, James Corden as Gary Barlow and stand-up comedian John Bishop as Robbie Williams.

And the REAL Take That were on hand to add extra Shine to the occasion.

Mum-of-one Catherine and Jason stayed in touch after the show and enjoyed a growing friendship.

They have been dating since the summer after the award-winning funnygirl split from her partner Twig Clark, a 38-year-old stage manager.

The pair have been seen on a string of dates including an overnight stay in Stratford-upon-Avon, where they watched the Royal Shakespeare Company perform A Midsummer Night's Dream.

They were spotted having lunch at a restaurant in the Warwickshire town, though they arrived separately to avoid being seen together.

An onlooker said: "They were trying to keep things secret but looked very loved up and happy together."

A friend added: "It's a very unlikely pairing but they have really hit it off.

"They've been on a number of dates to the theatre and the cinema. They really enjoy each other's company.

"Catherine deserves someone nice and she has landed on her feet with Jason. But they have both been desperate to keep their romance secret."

Catherine — also known for appearing in Dr Who as the Time Lord's companion Donna Noble — has been seen with Jason at a cinema and coffee shop in Kensington, West London, near the singer's bachelor pad.

They have also been to the National Theatre on London's South Bank. They were pictured together celebrating Walliams' River Thames swim at a London hotel last month.

And a source said Jason has been seen leaving Catherine's home in South West London on a Sunday morning. Twig lives half a mile away and he and Catherine share parenting duties for their daughter Erin, nine.

Jason has never been married — but has been linked to a number of women including Page 3 beauty Kathy Lloyd, singer Lulu and Wheel of Fortune star Jenny Powell.

Catherine met Twig when she was performing at the National Theatre and he was stage manager for her play.

She said at the time: "I distinctly remember the first day and him holding the door open for me. I remember thinking, 'Oh, they've got a YTS boy'."

But she has said of the age gap between them: "It's five years, quite a lot really."

The Sun revealed last year that Catherine was the target of a poison pen fiend who falsely accused her of cheating on Twig.

l.holmwood@the-sun.co.uk