Star rating: ***

A quick look round establishes the audience's suitability for this Christmas show in the Tron's Tall Tales series: they are all - adults excepted, of course - teeny-tiny and aged under five. Hurrah!

Little Rudi and his sister, Cupid, won't have to convince anyone of the essential facts in their story: that Santa Claus exists and has a sleigh pulled by reindeer which flies through the sky on Christmas Eve, delivering presents. Cupid (Jennifer Edgar) is already in Santa's reindeer team. But Little Rudi (Barry Henderson) is still waiting - hoping - to be chosen.

Since Rudi is such a lovable bright spark, we all want him to get his wish. So when he and Cupid ask for help in carrying out the tasks that will prove Rudi is brave, strong and kind - as listed in the reindeer job description - there's no shortage of pint-size volunteers, keen to be trees in a spooky wood or mystery presents waiting to be unwrapped. But Rudi's little black nose suffers various mishaps along the way, turning bright red in the process Will he be left at home on Christmas Eve?

There's a neat twist - depicted in some colourful video animation - that prompts the happy ending but, really, this isn't the kind of show that surrenders the story to screenplay.

This show is 50 minutes of cleverly structured, interactive make-believe, cheerfully guided by Edgar and Henderson in a friendly informal way that keeps the mix of listening and joining in lively - all helped by a few special surprises, nicely hidden away in the Christmassy props that make the Tron's upstairs space feel cosy and appealing.