Footage has been released which was recorded on one man's mobile phone as he travelled around the British capital.
It shows the man inspecting a number of key train and subway stations in the city, including Oxford Circus, in the heart of the retail district, and Liverpool Street, a main commuter terminal for people living in the suburbs.
Police said they believed information was being gathered for a possible terrorist attack in the capital or at major regional shopping centres.
Five men were arrested in July 2008, but none were ever convicted of terror offences.
The case led to the conviction of two Algerian men, both in their 40s, of running a mobile phone and luxury goods fraud racket. The pair served jail sentences before being deported.
He told police he was a tourist, but an inspection of the man's phone found up to 25 minutes of footage of Tube stops and other crowded places.
The Algerian national can be heard speaking in a North African dialect, which was later translated at one point as, "There are cameras there, there are cameras everywhere".
The footage has only now been publicised to counter a flood of criticism over police stop-and-search powers.