Ged McKenna works on the buses. But he’s not a driver or a conductor, he’s a London tour guide. He’s also an actor, like many of his 50 colleagues at the Big Bus Company, using his oratory skills to earn a living between jobs. So, for the time being, the top deck is his stage and the only time he takes a bow is to let passengers get a good look at a landmark.

He performs his two-hour soliloquy three or four times a day, keeping tourists entertained and informed on the 18-stop route stretching from the West End to Tower Bridge and back.

As the bus sets off from Green Park, Ged starts dishing out the fare - a full helping of history for culture-hungry tourists with a side serving of silly jokes. “The last deer to be culled in the park was in the middle of the last century,” be begins. “You will occasionally find the odd old dear in the park these days. But please don’t kill them - they’re quite harmless.”

Passing Nicky Clarke’s hair salon on the corner of Berkeley Square, he reels off a list of celebrity heads, adding: “He charges Pounds 190 for a trim. I haven’t spent that much on haircuts in my life, as you can probably tell. ”

And in Piccadilly Circus: “If you declare your love under the statue of Eros, your love will never die. Prince Charles told me that.”

Shirley from Somerset and her friend, an English teacher from Hungary, are impressed. “He’s good, isn’t he? We were going to get off at Buckingham Palace but we’ll stay on now.”

It turns out Shirley has an ulterior motive for prolonging her journey. Her son designed the gates guarding Downing Street. “I’m very proud of him, ” she glows.

Meanwhile, Ged is distracting his anorak-clad audience from the grey clouds gathering overhead by filling them in on the finer points of royal history: “Charles I was only 4ft 11in,” he informs us at Horse Guards Parade. “But he was a lot shorter when they cut his head off.”

When the heavens finally open outside St Paul’s Cathedral, he quips to the departing passengers: “Don’t pray for rain.”

In among the well-informed factual commentary and the jokes, there are some gems of information. Did you know that Waterloo Bridge is known as the Women’s Bridge because, when it was completed in 1942, most men were fighting in the war so the labour used to build it was female?

Or that the multi-tiered spire of St Bride’s Church off Fleet Street inspired the traditional wedding cake design? Or that there are more than a million works of art in Buckingham Palace?

As the tour comes full circle, Ged uses his 15-minute break to get some liquid refreshment. Such a long running commentary can take its toll on the larynx.

He admits he didn’t know a lot about London until he received a six-day induction course from the Big Bus Company’s “frighteningly knowledgeable” guide trainer Robert Goodman, who encourages a lively style. “You have to give people an entertaining time, ” says Robert. “If it’s dry as dust, that tends to bore them.”

Originally from Liverpool, Ged came to the capital in 1982 to go to drama school.

Having a trained voice has helped - even with a microphone, making yourself heard above the traffic can be difficult.

“You’ve got to have a voice that will last all day in this job. The average speed around London is nine miles per hour, so you’ve got plenty of time to see everything. Traffic jams are the worst - you’ve got to have a store of anecdotal stuff. You get maybe three or four of those on each tour.”

Ged is off to Japan in September playing Trinculo in The Tempest. “It’s the part of a jester and this is great training. You have to be smiling all the time, even if you don’t feel like it, a bit like a tour guide.

“Sometimes foreign visitors are a bit put out that I don’t speak their language, but I just take it a bit slower and try not to patronise the English speakers.”

In between treading the boards at venues as prestigious as the National Theatre, Ged has done jobs in factories, painting and decorating and gardening. “People ask me all sorts of questions in this job. But I’m used to that. ”

“Resting” can be hard work. But Ged hasn’t left the acting fraternity behind entirely - his driver is called Robert Wagner.