A subsequent search today revealed that the bird was indeed a Dusky - London's first! What an amazing find!
I most admire the fact that Lol was willing to be called a fool. He could have quite easily seen the bird, felt uncertain about it and kept his trap shut thus preventing the potential rediscovery of this great bird. He now has been given the freedom of the city.
I guess the message is don't be afraid of making mistakes and have trust in your instincts.
I myself have not seen a Dusky Warbler and I am dead keen to go and see it tomorrow, but I've just realised that I haven't got the time tomorrow. I just hope that it sticks around for a while.