This is Heron House, a 100K SF office block at Albert Square, Manchester.

Almost everybody knows that the government's secret communications agency, GCHQ, has its Northern base in the Manchester City Council-owned block. But very few people know of another secret occupier, the little-known but important Office for Communications Data Authorisations. Thanks to an over-sharing fit-out contractor, we also know what it looks like, Secret Bases reports.

The Office for Communications Data Authorisations is a branch of the Home Office intended to oversee who can intercept email and online activities and telecoms, and who cannot. As a regulatory body it is unusual to find it co-located with one of the organisations it might have to regulate, like GCHQ.

The same source suggests that GCHQ already have a facility close to Manchester Science Park that hosts a hacking team, better known in the security world as a Computer Network Exploitation team.

The interior fit-out of the OCDA office shows a bright, light call-centre type environment with little scope for personalisation at workstations, and plenty of discrete but still visible video surveillance.

A further set of pictures released by Secret Bases shows the (also discrete) but serious security at the entrance to Heron House.