In reply to drunken monkey:
>
> I'm no expert, but it was pretty distinctive - Dark grey and white, and had a distinctive long feather in the centre of its tail. Certainly looked like the pictures on the RSPB website. About the same size as a large gull.
Certainly sounds like one.
They fly in a very falcon-like way, and would seem like a turbocharged gull in flight.
> I hope it wasnt hoplessly lost.
If it was flying around the SNS, I'm thinking it probably was