The vet was very reassuring, and said that, although there was a risk with the anaesthetic because of Sylvester's age, he definitely stood a good chance of making a full recovery.
He was given a sedative (the cat, not the vet!) and I left with instructions to call after 2pm.
Sadly, the people at the clinic called me back at about 12noon to say that Sylvester had passed away. Although he'd started to recover from the anaesthetic and seemed to be ok, they thought his heart just gave out... and they reassured me that he would have been so zonked with the painkillers that he wouldn't have been in any distress.
So, it's RIP Sylvester... I thought I'd share a few of the photos I have of him.
Many thanks for all the messages of support, prayers and best wishes for him over the weekend - they're much appreciated. Normal non-cat-related blogging will recommence shortly...