The vet has phoned with the results about the lump on William's tongue. It was a type of cancer called a Plasmacytoma, which surprised me slightly because both vets that had seen it thought it more likely to be benign.
However, the good news is that the vet has told me not to worry because it was caught early so is very unlikely to have spread, and he removed a large enough area around it to be as sure as he can be that he removed all of it. He sounded very positive, and I know him well enough (and he knows me well enough) for me to be sure that when he told me not to worry he wasn't just saying that to reassure me.
I'd much rather it wasn't cancer of course, but I feel very lucky that I noticed it when I did and while it was still so small.
So I'm hoping that it's now gone for good and never returns. I'll check William's tongue every few weeks or so from now on, just to be on the safe side, and whenever I take him to the vet for anything I'll get them to check too.
Will is absolutely back to normal now, but very bored because I haven't been taking him on his daily New Forest walks because of the stitches in his tongue. He loves nothing more than picking up sticks and carrying them round, sometimes chewing them too, and I don't think that's wise while his tongue is still healing.