ALAN Titchmarsh ditched his gardening boots and put on his train driver's hat for Nature of Britain.

He took the controls of a tank engine at Didcot Railway centre for a piece of film which will be shown on BBC1 tomorrow, and repeated on Sunday.

Mr Titchmarsh - who spent a day at the centre in the summer - will be telling the tale of the plant Oxford Ragwort, senecio squalidus, whose seeds were spread from Oxford to London via the railway.

A native of Sicily, the ragwort was grown in the Oxford Botanic Garden, but seeds escaped and the plant became common on the walls of the Oxford colleges.

When Oxford became a railway centre the plant colonised the clinker of the railway beds and its seeds were transported all along the rail network.