Transocean has a sizeable presence in the North Sea, with more rigs operating than in the Gulf, although they are mostly at shallower depths. Led by committee chairman Tim Yeo, a former Conservative environment minister, the MPs will ask how many rigs operate with only one set of "blind shear rams" inside their blowout preventer, the last line of defence against a major spill. The Deepwater Horizon's single pair of shear rams, which are supposed to cut through the pipe to close off the well in the event of a blow-out, failed to activate. Transocean's new rigs are built so that they can accommodate two sets of blind shear rams, which make such a catastrophic failure less likely. But UK regulations do not require operators to use blowout preventers with two pairs of blind shear rams. A spokesman for the Health and Safety Executive (HSE) said yesterday that the rules were "goal-setting and not prescriptive".