Donning a white beard and red tunic to impersonate Father Christmas may seem simple enough. But according to Clifford Hume, a professional Santa lookalike who trains squads of St Nicks for grottoes in Britain’s department stores and shopping centres, the role requires far more than twinkly eyes, an ample tum or a fruity laugh.

To work with children and keep your beard intact while at the same time conveying the pure magic of Christmas takes the patience of, well, a saint.

“This lovely little girl picked a poster out of my bag and promptly poked me in the eye.” he says.“I had blood trickling down me and I had to be nice to her. It is very difficult to do.”

For 10 months of the year Clifford is a professional performer, master of ceremonies and cabaret artiste. But from the beginning of November he becomes “Professor of Santaology” and trains new recruits at the Ministry of Fun, an entertainment agency in south London.

Inevitably, many applicants are actors - the company advertises in The Stage and in the Oldie magazine. Playing Santa in a grotto can pay up to pound;150 a day.

The agency does boast one former policeman, though sadly there are no ex-teachers on its books. Perhaps they feel they have done their bit or have lost the ability to beam unconditionally at small children.

“It is not just about being an old bloke with a beard,” says James Lovell, who runs the Ministry of Fun with fellow performer Julian Pearson. “You also need performance skills.

“You cannot be an old misery, or boring. Children need to have a special experience when they meet Father Christmas.”

Having your own white beard is optional, corpulence is not necessary and even youth is no barrier. Some Santas are in their 20s and the Ministry can work wonders with make-up, spirit gum and padding. But one key quality they look for in applicants is in the eyes.

“They need to have sparkly, festive eyes, a big smile and a nice rich voice. Some of our Santa lookalikes wear fake stomachs. A shocking revelation, but obviously the real Santa is chubby,” says Lovell.

Applicants are invited in for an interview. “First of all they have to be charming, nice and jolly people. They must also like children and be able to interact with them.

“If a child comes in and is quite nervous or shy, quite often they don’t say anything at all. So you need a bit of a spiel so everyone in the room can relax, and gradually the child will start talking to you.

“When people come in for interview, we can decide quite quickly whether they are going to be any good or not.”

The agency has some 20 Santas on its books and they all have to undergo police checks. It also hires e lves, although these tend to go under the rather less Tolkienesque title of “Santa’s Helpers”. And forget cute little people in green tunics stuck in a cavern in the frozen North making toys. Today’s helpers have to be multi-skilled in everything from magic tricks and juggling to placating those in long queues outside the grotto, to cheering up a reluctant child.

“You cannot force a child to go and sit down next to Santa. They have probably never before seen a man dressed in red with a big beard and a big loud voice. So there is a certain skill in introducing children to Father Christmas.”

Training begins in early November with the outfit and how to wear it. It is not a case of simply putting it on and striding around going “Ho-ho-ho”. There is a degree of method acting involved - you have to adapt to the role.

“I remember the first time I did it,” says James Lovell. “You sit there thinking crikey, I’ve got the costume on. It is a very strong look. There are certain looks as a performer that really work - people respond very well to a clown or jester for instance.

“As Santa you are very clear who you are. So you are sitting in a grotto and the door opens and the child comes running in, stops, and their jaw drops to the floor. They cannot believe Father Christmas is there. So you have to be very responsible and true to the character, without wishing to sound too much of a luvvie.

“Children think Father Christmas is something incredible. So it is important that they meet you and leave still with that feeling.”

During a day or two of training, the Ministry of Fun puts its rookie Santas through real-life scenarios, using actors to play bolshie or terrified children. Tutor Clifford Hume has a personal interest in Christmas folklore and traditions.

“To be an effective Santa lookalike you have to know the history of who Santa was, and the history of Christmas itself,” he says.

Trainees learn that the real St Nick was born in year 270AD, nowhere near the North Pole but actually in a part of Asia Minor (modern-day Turkey, appropriately enough).

His father died when he was young and left him a fortune which he began to give away to the needy, particularly children, which earned him the title of Gift Giver of Myra. On his death he was made a saint for his kindness.

Trainee Santas also learn how he is regarded in other cultures.

In some countries he is known as the Rider, in others the Ash Man because of his predilection for chimneys, and even Shaggy Goat because of his appearance. The modern Western image was influenced by a 1931 advert for Coca-Cola.

New recruits also get a grounding in the practicalities of the job. It can be exhausting remaining cheerful in a grotto for six hours a day.

You have to keep up with all the best-selling toys, and who is the latest winner of Pop Idol; you are even taught how to avoid being unmasked should a child suddenly make a pass at your beard.

But, at the end of the day, a Father Christmas lookalike has to be able to convey that certain festive magic.

“He has to be kind, considerate and a good listener,” says Clifford. “Basically he has just got to be magical from the moment that the child walks into the grotto.”