Martenkay - I read that linked page, thank you. The sarcasm was peaking there, too. So funny. I'll assume that the medals are rusting, I think, and use a 'rust converter' and some other coating, maybe.
Thanks for the replies, even the sarcastic ones. Hahahaha. The ones hat have tarnished seem to have had a brass coating over alloy which is rubbing, fading away. I keep them only to remind me that I actually ran on those days, as I've got an atrocious memory. And, some look pretty cool. Ever since my niece looked at them and thought they were amazing, and now wants to run too, I've decided to keep them. Until then they were just to remind me of good times.
I haven't run for 2 years and I'm nearly wetting myself with excitement for this event. I love this run. I remember running through the city centre previously (through The Hayes). It was amazing to see and hear thousands of people running through the pedestrian areas. It was excellent. There were a couple of annoying (and seemingly pointless) bottle necks, but, I liked the flyover bit. I quite like a route change too. I wish they would bring back the marathon and let the finish line be within the stadium again. Wow. It was perfect.
The best marathon I've done is London, and Cardiff is the best half marathon. The complete worst was Victoria Falls. That's what put me off for two years.