IT RESEMBLED a cinema, and commanded stunning views of Portsmouth, the Solent and the South Downs, but the 'Portsdown Odeon' will soon be a memory.
The demolition of Portsdown Main, a 1950s Art Deco building once used by the MoD for advanced radar production, began on Thursday.
And Portsmouth architect Mick Morris said it would be a sad loss for the city.
Mr Morris, whose work in Portsmouth includes the conversion of 1 Florence Road, Southsea, said: 'It's the Odeon of Portsdown Hill and it's a great shame it's going.
'All the buildings on Portsdown Hill are wonderful, quite exciting. It's extraordinary to think what it was used for, considering its design, it's a stunning building.'
Portsdown Main was designed in the 1930s, but was delayed by the outbreak of war and was not built until 1952.
It was used by Admiralty Signals Establishment, the Admiralty Surface Weapons Establishment, the Defence Evaluation and Research Agency, and then by the Defence Research Agency, until its doors closed for the last time in January 1997.
It is owned by the Defence Science and Technology Laboratory, part of the MoD, which has admitted defeat in its attempts to sell it, after a survey pronounced it structurally unsafe.
Mr Morris accompanied a client interested in buying Portsdown Main on a tour around its inside.
He said: 'It was a really striking building, just rising out of the hillside.
'Inside, looking out, you could see across the city of Portsmouth and out to sea, then in the other direction across the countryside.
'Everything about it was unusual. It's a shame it's going. It will be missed, and I don't imagine anything that replaces it will be as imaginative or as striking. It should.'
DSTL estimates the demolition, including returning the site to farmland, could take until September next year.
The firm says it has not planned a replacement, but will consider ideas as the demolition progresses.
Councillor Luke Stubbs, who worked for seven years at the adjoining Portsmouth Technology Park said: 'It's a local landmark and one of the few buildings in the city that could be fairly described as iconic. It's part of Portsmouth's military heritage. I had assumed it was protected, but it's not.'
And Councillor Jim Patey, whose Paulsgrove constituency is overshadowed by Portsdown Hill, said: 'It's a landmark and it'll be strange for us here when it's gone.
‘It has been empty a long time, but I think it'll be missed.'
Caroline Deane, a spokeswoman for the MoD's defence estates, said: ‘Work has begun to demolish the building, because although there were plans to see if it could be used for anything else, it was declared unsound.'
‘It's a local landmark and we understand people will miss it, but it was unsafe, so it has to come down.'
Demolition begins of MoD's art deco Odeon
Cinema-like building left empty for a decade will be gone from Portsdown Hill by September 2011