Last night when walking the dog I saw a pure white bird flying in the sky above me. it was really noticable as the sky was pitch black. The bird was completly silent and probably about twice the size of a crow. Can anyone tell me what bird this was as I'd really like to know.
 I am located in North Yorkshire, just on the edge of the peak district in England. I estimate the time of the bird sighting to be around 10pm in the evening, it was very dark out, although we do have alot of snow here at the moment so appears to be a little bighter than normal. The Birds wings appeared quite wide and twice the length of the body. The most striking thing about the bird was how white and bright it appeared in the sky.

It is possible it was just a seagull but with the very clear sky and half moon the moonlight made it appear unusually bright and white.

Seagulls' wings are not very wide, though.  Could it possibly have been a snowy owl?  Wikipedia says that "Between 1967 and 1975, Snowy Owls bred on the remote island of Fetlar in the Shetland Isles north of Scotland, UK. Females summered as recently as 1993, but their status in the British Isles is now that of a rare winter visitor to Shetland, the Outer Hebrides and the Cairngorms", which suggests not, but I suppose it's possible that one came further south that usual.

I think the trouble is that quite a few birds might answer your question! Could it have been an egret? They are very bright white and have a wide wingspan, but should have legs trailing behind them that you might have been able to see, even if it was dark. They are not nocturnal, but many birds will fly at night, particularly during migration.

Barn owls are usually culprit, especially considering where in the country you saw it.
The bright white, even on a dark night is typical and their long, broad wings make them look big. Alternatively, a little egret is not impossible, esp if it was moving through with the cold weather but I suspect the barn owl is more likely. A good spot - hope it finds food during the snowy weather.