If you have spare time having arrived at the source I recommend walking ahead and left along the former canal to the Tunnel House Inn.
Christopher Middleton has rightly given it a rave review in today’s Daily Telegraph.
I don’t mention it in the Thames Path guide although maybe a I should in future. The route from the source features in Pub Walks Along the Thames Path (Countryside Books) if you can still find a copy.
See page 213.