Among other things, (which hopefully we will find out about), I believe it was used to provide a subject for the NATS official photographer. A black-and-white image of this radar features extensively in the Wolff-Olins NATS 're-brand' that occurred during the 'Red Barron' era.
I always wondered which radar it was as it's mounting is unusual.
Its picture appears at least once in the corridors at nPC and also adorns the ops-room wall just behind the stationery cupboard at the end of the W2 LAG.
I think it was an HSA 23cm radar head, similar to the one at Heathrow.