Message received from an agility friend of mine, Eton Rowing Lake is also known as Dorney Lake which is where she was, but then toads can be near any water...
BEWARE: while walking at Eton Rowing Lake, my healthy dog Marmite became acutely ill, unable to walk and vomiting. She was in the vets within the hour, by the time i got her there she was not responding, drooling excessively and twitching. ...I thought she was going to die. She was put on a drip, blood test etc. All the signs pointed to poisoning from contact with a Toad. Thankfully she is now home. (first aid-rinse out dogs mouth asap)
Zab