I regularly travel to St Petersburg, Russia, and in the middle of the day local time a lot of this traffic, maybe a dozen or more per day, tends to come westbound overhead the city (eastbounds pass at night there). In the clear northern air in summer the 747 contrails seem particularly vivid and long-lasting. There's no Russian traffic on such a route (indeed, you never see Russian aircraft over the city, likewise Moscow) and some discussion here on PPRuNe a while back showed me it was Japanese/Korean/Chinese traffic to Europe.
Some days there is nothing, I guess it just depends on the winds aloft which of the tracks is most favourable.
Normal route from St Pete to London is direct Copenhagen direct Clacton.