After a tip off from Wanstead, I was out in the garden at 21:00 waiting for the predicted flypast of the International Space Station. It was supposed to appear at 21:03, by 21:04 I was becoming doubtful but 30 seconds later it was there, cruising serenely Eastwards.
According to Wikipedia 'the station is maintained at an orbit between 278 km (173 mi) and 460 km (286 mi) altitude, and travels at an average speed of 27,743.8 km/h (17,239.2 mph), completing 15.7 orbits per day', apparently.
I just thought Wow! as it went over.
Can you tell what it is yet?