Now......I recognise that one. Back in the Seventies, I completely overhauled one, right down to the bare chassis. Although it is down as a Bedford R type, it is in fact a 4x2, so an S type. This always puzzled me because the S was discontinued around 1959 when the TK came along. The R type 4x4 continued until about 1979, but this sweeper was built in the mid-60's. Anyway, it was a bit of an animal to operate as the sweeping attachment was belt driven of the back of the gearbox, really sapped the power.
There are numerous cloth bags inside that are filters, a long handle on the side is attached to a shaker mechanism inside so that the dust can be shook off the bags.
The rear view mirrors on top are something else, imagine seeing a Vulcan approaching from behind!