I’ll just chime in and say there is definitely something wrong with Greater London. Take a look at my run in London Marathon, and pick Woolwich Church Street.
I’ve just sent in each of your accounts in this thread for reprocessing - that’ll fix the issue for each of you. It’ll take a while to finish - there are ~10k activities to work through.
I’m pretty sure the issue is caused by failed syncs, but I haven’t filled figured everything out yet.