Surely this is public property...?
Originally The Post Office and inherited by BT - what right have they to sell it? 
When the Government first caused these places to be built various departments were involved. Over time, as those departments have waxed and waned, bits have been hived off. Responsibilities have been shuffled to hide maintenance costs and the like in various budgets. Much of the "secret" stuff ended up the responsibility of the Post Office, which was a natural home as the PO also looked after radio, radar and telecommunications as well as TV and Dog licensing.
In the early 70s British Telecom was created and split off from the Post Office as a first step toward privatisation. Budgets and financial responsibilities changed dramatically and many old PO tunnels and "research establishments" were transferred to BT. As privatisation took hold so the issue of these "facilities" became ever harder to hide in the accounts. As with any land, building etc they had to have a "book value" and the maintenance costs had to be declared. Nobody argued and frankly the Civil Service were glad to get shot of the problem so BT ended up as the owner of a great many redundant premises. Many of these have been let out over the years to a wide variety of businesses. One such, that I have a good knowledge of, was for some considerable time used as a research and development centre by Cadbury (later Cadbury Schweppes) where they developed a number of new products. It is actually just off the North Circular Road, not far from Staples Corner. A labyrinth of buildings, Nissan huts and tunnels that has now been sold off and converted into an industrial estate but as late as 1993 it was still a closely guarded secret with a substantial security bill paid by BT ~ Cadbury Schweppes being the acceptable public face of the site but in reality they leased only a small portion of it.
Coming up to date Nulabour having
accepted wholeheartedly embraced Conservative notions of market forces and privatisation and having the usual Socialist attitude toward national security and our history are cheerfully selling what little of the "family silver" is left ~ reasoning, no doubt, that if a plastic spoon is good enough for their mothers it is good enough for the rest of us (although they personally wouldn't be seen dead with a plastic spoon). Cash raised by such sell offs will go a long way to covering up Brown's mistakes.
