National treasure Christopher Biggins is holding court in the magnificent central London rooftop bar of the Trafalgar Hotel.

Resplendent in yellow jacket, straw hat and blue suede shoes, he effortlessly entertains us all with his stories, makes sure we are suitably refreshed with drinks as we all bask in the sheer delight of being in his company and listening to his good-natured banter and unmistakeable, high-pitched laugh.

And it is the warmth and expression in those distinctive tones of his that will help to make one of his latest ventures a success.

He is the narrator on a number of new self-guided walking tours of London available from Cities Talking, an idea from Chris’s friend, Julie-Anne Uggla, that take listeners through the fascinating, history-filled streets of our capital city.

As Chris leads our small group of journalists from Trafalgar Square along the Strand to St Paul’s Cathedral, listening avidly to his own commentary on headphones, it’s clear to see that he is fascinated to hear all the anecdotes and little-known facts about the landmarks unearthed by the brilliant comedian and writer Kathy Lette, who penned many of the tour scripts.

He was particularly interested in the accounts of public hanging at Tyburn and cheekily admitted that if they were held nowadays he would be an eager spectator, just as we hear Nell Gwynne, Charles II’s earthy mistress did too. The commentary on our audio guide describes her as “a 17th century Cinderella…..well-known for her love of cockfighting, gambling and swearing.”

As we took a mid-tour rest in the quaint, tiny and surprisingly empty Nell Gwynne pub, found down a tiny side street off The Strand, Chris, who lives in Hackney, says he loved recording the four tours and adds: "I never have time for walking tours like this but I've learnt so much about London. It's fascinating."

He says he gets his most intriguing views of London when he drives around the streets in his convertible car. But admits a love of travel and tells us all that we should visit Venice, one of his favourite cities.

The I’m a Celebrity… winner also loves Malaysia and is off on a trip to Vietnam in the near future. His ultimate break however, he says would be a luxury transatlantic cruise to New York.

Conversation then went from stories of Ronnie Barker and Richard Beckinsale, Chris’s fellow actors in Porridge, to his roles in I Claudius and the Rocky Horror Show.

Needless to say the whole pub was enthralled.

Although he doesn’t frequent pubs very much, Chris says he loves having dinner parties at home catered by his partner Neil “a wonderful cook”.

When he does go out he prefers to spend his evenings in restaurants, such as Jo Allen's in central London and is teetotal nowadays after dropping his two-bottles-of-wine-a night-habit when a dear female friend of his died of a drink-related illness.

Sipping his Diet Coke he says: “I was so angry with her, she was far too young to die.”

As we leave the pub the tour app cleverly picks up our position in The Strand on GPS and we continue to hear all about The Savoy Hotel and The Savoy Theatre.

Chris stopped here for quite a while, fascinated by the stories of Gilbert and Sullivan musicals and the famous American Bar where Hollywood legends such as Katherine Hepburn, Errol Flynn, Charlie Chaplin and Marilyn Monroe hung out when they were in town.

We then stroll by the Wig and Pen Club, Somerset House and Fleet Street, the Old Bailey and on to St Paul’s Cathedral where I reluctantly part company with Mr Biggins with kisses just like old friends.

It’s been pure pleasure to be in his company. Try the virtual version for yourself and you’ll feel the same way and learn a lot too.

The Cities Talking app has pause-play options and can be downloaded to run straight off the phone without the need for mobile data. There are 40 customised tours across 28 cities, including Amsterdam, Istanbul, Berlin, New York, Paris and Prague. You can add your own tour notes along the way and, using the ‘FYI’ function shows you the best places and tips on where to go in the city.

Christopher Biggins also narrates: London: Power and Places; London: Art and the Underworld; London: Kings and Democracy.

The Cities Talking app is available to download for free in the Apple App Store and Google Play. Tours cost £4.99. Details: www.citiestalking.com