No it was not a nuthatch. In fact, a nuthatch came and sat on the rail just after the anamolous tit, and I know very well what they look like. After a good browse on the internet, I am perfectly sure that what I saw was a coal tit with a long beak, there are many films and photos of mutant tits with long beaks to be seen on the internet. This fact was not in any of my bird books.