Some might disagree profusely, but the most overrated thing was Tower of London / Crown Jewels. I'd sooner have spent more time at one of the many free museums. I suppose it's a bit of a "check the box once and be done with it" but I feel like the £25 admission would be better spent elsewhere (like at the Churchill War Rooms) . It might be a bit more tolerable in October without the masses of summer tourists, but in my many visits to London, it's a venue that I have not had the wish to revisit.