Garry I suspect the contractor was referring to the New Roads and Streets Works Act, which is the 'bible' for contractors working on or about the public highway.

Garry what you say is quite correct, indeed it is a legal requirement under The H&S (Safety Signs and Signals) Regs 1996, reg 4(6)....pasted below: "(6) Where it is appropriate to provide safety signs in accordance with paragraph (1) because at a place of work there is a risk to the health or safety of any employee in connection with the presence or movement of traffic (including pedestrians in relation to such traffic) and there is an appropriate sign in that connection prescribed under the Road Traffic Regulation Act 1984, that sign shall be used whether or not that Act applies to that place of work." Having said that I think it would have to be a very petty enforcer to get too wound up if you were using an alternative sign that was patently fit for purpose. The RTRA 1984 doesn't actually prescribe the signs, that is done by subordinate regs The Traffic Signs Regulations and General Directions 2002 [warning a fairly large download!] Hope this helps