Pedestrian and cycle access is now prevented for security reasons - registered vehicles can be monitored through the ANPR system in place outside of the tunnels and inside the central area. The cargo tunnels are still used with their apron access shafts continuously monitored for security breaches. There are other tunnels as well, which may be what has been alluded to in earlier posts, which were opened again a few years ago during the construction of the new T2 after many years of disuse to reveal some interesting historical artefacts from LHR's past.