www.bbc.co.uk/news/uk-21345730
Just in case anyone hasn't had theirs done. It applies to every dog, both old and new :) and don't forget to update your details if you move house / change vet!
I hadn't realised it was being made law that dogs must be microchipped (mine were done as pups several years ago) but I think it's a good thing - hopefully it might lead to fewer strays and lost / abandoned animals. Although I suppose if you're the kind of person who'd abandon a dog you probably wouldn't be the kind of person to get it microchipped anyway... Time will tell!