Rust never sleeps

So, I was two thirds of the way through the mowing this morning (a jungle had formed during our two week absence) when this happened. We've had this mower for about 12 years. It's seen service in four different gardens and only cost £50 when purchased new. It's been like a good friend. It has always started first time no matter how long it's been between mowings except for once, about six years ago. I took it to a mower guy and he serviced it. Interestingly, I have never put oil in it. The new one just doesn't come close to replacing him.