Its about knowledge, how we perceive it and its necessary limitations. The play is static, it is all conversation, there are no scene changes and the characters dont go on a journey or develop. There are characters from 1809 and characters from 1993 when the play was written. In 1809, Thomasina Coverly aged 13 (Dakota Blue Richards) is being tutored by Septimus Hodge (Wilf Scolding) who she teases into explaining the meaning of a carnal embrace. Bright Thomasina is a maths genius who has worked out that all matter conforms to a pattern of numbers. She says we can decode the numbers that make a leaf leaf-shaped. However, not only does she not have enough years left in an entire life-time to write these numbers, she would never have enough notebooks. Also, explains Valentine Coverly (Ed Macarthur) in 1993 you would go insane. Today the job can be done with a computer. Conversely, Thomasina notes that we cannot undo the past by trying to reverse processes. Hearing what she is about to have for dinner she says that when you stir the jam into your rice pudding, the jam doesnt go back into a blob if you stir it the other way. In other words, we cant work history backwards. There is no mechanism for it. We will never really know whether Richard III killed the Princes in the Tower. The 20th century historians in the play can only guess whether Byron killed another poet in a duel. The humour in the play comes from how the characters in 1993 get it wrong when they make discoveries from 1809, which we see before our eyes. This is a lively production with some strong performances, particularly from Dakota Blue Richards, Kirsty Besterman as Lady Croom, Thomasinas mother and Robert Cavanah as Bernard Nightingale, the modern day literary researcher. Its a play about learning. Do your homework before you see it. English Touring Theatre present Arcadia by Tom Stoppard at Cambridge Arts Theatre until Saturday, April 4.