Oh wow, got back into Exeter, parked up where I usually do, and my dad asked me to drop him back home, since he was knackered. I started up, got 500 yards up the road and the engine cut out. Ok, so it's stalled. Turned the key, and the starter motor spun happily but the engine would not fire. At this point I just laughed, we pushed it into a parking space off the road, locked up and walked home.
Earlier today I had replaced all the spark plugs with brand new ones, and I reckon one of them I didn't tighten enough, so it steadily shook loose, and the last speed bump loosened it enough for the engine to die. Will fix tomorrow. Funny though since I had already parked up and was just doing an extra bit, so it didn't matter in the slightest that we'd broken down.
Again, human error. One can tinker too much.