The difference is more than you might think - it's about 99.2 C at London's highest point, on the North Downs above Westerham, slightly south of that odd Shampan at the Spinning Wheel restaurant. Which is just higher than the Shard's observation deck.
Edit: At officially 245 m it's almost exactly the same height as the Shard's observation deck at 244m.
The difference is more than you might think - it's about 99.2 C at London's highest point, on the North Downs above Westerham, slightly south of that odd Shampan at the Spinning Wheel restaurant. Which is just higher than the Shard's observation deck.
Edit: At officially 245 m it's almost exactly the same height as the Shard's observation deck at 244m.