Highest barometric pressure
Russian Federation (Agata,Siberia)
The highest barometric pressure ever recorded was 1083.8mb (32 in) at Agata, Siberia, Russia (alt. 262m or 862ft) on 31 December 1968. This pressure corresponds to being at an altitude of nearly 600 m (2,000 ft) below sea level! Made more amazing by the fact that the place where it was measured was 262 m (826 ft) above sea level!
The highest in Britain was 1054.7mb (31.15 in), in Aberdeen on 31 January 1902.
Barometric pressure is the physical pressure exerted by all of the air above you. Naturally as your altitude increases, the pressure goes down, as there is less of the Earth's atmosphere above you to weigh down on you.