Whatever three men in a boat can do, two girls in a canoe can do better - that is the claim of Lindsay Dean and Heather Rand, who are aiming to paddle their boat from the source of the Thames all the way to the sea.

They plan to take about a week to do the 150 miles with its 50-plus locks, starting on Saturday. Their feat will raise money for two autistic children in Watlington who they help care for, to send them to the Autism Treatment Center of America.

Lindsay and Heather, both 25, live at Watlington Hill Farm, Christmas Common, and both went to school at Watlington Primary and Gillotts School, Henley. Both work caring for people with learning difficulties and autism. Ms Rand said: "We hope to raise more than £1,000 for the Laura and Stevie Fund to send Laura and Stevie Bannister, aged six and four respectively, to the treatment centre. We will go from Ashton Keynes in the Cotswolds to the tidal Thames at Teddington Lock. People have called us inspired, intrepid - and insane."

The canoe is an Old Town Discovery 174 called Dedwyddwch, which is Welsh for Happiness. The two women have done a little canoeing, before but not long distance.

They are currently doing capsize practice in a swimming pool to be able to cope if the boat does turn over.

To sponsor their mission, go to www.source2sea.wordpress.com