My first professional panto was Aladdin. Three performances a day, directed by Miss Mina Shelley, who claimed to have been a principal boy in her day. At the time she was in her late seventies. The Dame had been a variety star, coming out of retirement for bits of telly. He was interested in red-haired, big-breasted women, and in horses. He wouldn't rehearse but in the half hour before the pubs opened, he would walk me round the stage muttering: "You say something. I'll think of something and then I do the business with door and shoes." So began my training in the art of panto.

Panto is as English as the gap in Terry-Thomas's teeth but my first exposure had been down under, as a babe in the Australian bush. It was a topsy-turvy Christmas in sweltering heat. Aladdin's Cave was in the cool under the house and Sleeping Beauty awoke to a new life on a verandah with citronella lamps to keep the mosquitoes away. An old lady who, it was said, had played for Tommy Beecham was in charge of the music. Vince the plumber told the same jokes every year and how we laughed. No amount of drought and heat or drudgery could dispel the contagiousness of joy. You never grow out of it.

Memories such as this, the child in him as in me, prompted Sir Ian McKellen to follow The Lord of The Rings with the Dame in Aladdin, the panto I wrote for the Old Vic. As a lad in Lancashire, his father, a shire engineer, had taken him backstage into the painted, panting beast. It was the desire to recapture the magic of his boyhood and pass the indelible experience to his own "children" - the young fans of Gandalf for whom theatre is less potent than Gameboys and computers - that led him to me.

Ian remembered I had written a panto, The Swan Down Gloves, for the RSC in the early Eighties and asked me to join his team. I knew that would be like doing the Christmas pudding - everyone gets to stir.

Panto has one vital ingredient - you, the audience. The English audience are the best-rehearsed members of any production. In Aladdin they are vital at the call to power up the lamp and again when Abbanazar tries to steal it. The audience call out a warning. At the Old Vic, they down the Villain by summoning his demons.

In this darkening world, it is a good thing to recall the themes of 1001 Nights - the transforming power of love and knowledge, the sustaining energy of peace and

starry-eyed panto lover

In Aladdin, the ching of cash registers contrasts with the spiritual wellbeing found in the Cave. Trapped in the darkness, contemplating his own rotting skull smiling among the sapphires, Aladdin realises that diamonds and pearls are not worth one breath of life and that he is a poor boy in a mine of rubies. Most of this is lost in a scramble to get the lamp and get to the interval for a pee and ice cream.

There are three other important elements to a successful show. A good villain is quintessential, while the Dame provides energy, personality, star power, laughs and frocks. In Aladdin she also has a key dramatic scene when, in Act 2, she gives the lamp away. The Dame should provide sexual glamour at its most outrageous. She shares this dysfunction with the principal boy who in most pantos is played by a girl with sensational legs and, in some cases, great breasts.

In traditional pantos, her sexual ambiguity was a box-office magnet. Now there is so much cross-casting that it has lost much of its pulling power. A good panto begins earnestly and innocently to retell a great fairy tale but it can go off in all directions. Ian has a childlike wonder. His love for panto means that he applies himself to the work with the same seriousness as he would a great Shakespearean role. This week he is doing the demanding tragic role of Widow Twankey. He will probably do Lear next. His Dame is the perfect warm-up to crack your cheeks.

Aladdin is at the Old Vic until 23 January, 0870 060 6628