MichaelJP wrote:
Why do the authorities feel it necessary to seal off such a large
area when they have already made the bomb safe and removed the
explosive material?

What area is sealed off? The RAC traffic report seems to indicate that
it's just the southbound route from Piccadilly Circus to Trafalgar
Square via Haymarket that is closed, and the BBC has reported that
Piccadilly Circus tube station has reopened.
--
Richard J.
(to e-mail me, swap uk and yon in address)