So it's Norman driving that speeding transit which always seems to be tail-gating me, is it?
A Transit is classified as a 'goods vehicle' and not as a 'car derived van' (such as an Escort van). As such, the speed limit for a Transit on a single-carriage road (where the National Speed Limit applies) is 50mph (and not the 60mph which applies to cars).
On dual carriageways, the speed limit is also 10mph lower than that for a car. i.e. the speed limit is 60mph and not 70mph.
It's only on motorways that the same limit (i.e. 70mph) applies.
For confirmation of the speed limits, see the Highway Code:
http://www.highwaycode.gov.uk/09.htm#103
For confirmation that a Transit is classed differently to a car, see this page (which is endorsed by Bedfordshire Police and the Highways Agency):
http://www.drivesafely.org/safety_cameras/spee d_limit_table.htm
Chris