THE Tube regulator was urged to grill London Underground bosses on safety issues last night as power technicians prepared to walkout on an eight-day strike.

London Underground power technicians represented by Unite, RMT and TSSA commenced strike action from 8pm last night over attacks to their working conditions.

Unite regional officer Hugh Roberts wrote to Office of Rail Regulation (ORR) chief executive Richard Price yesterday to seek assurances with London Underground management that their contingency plans are robust enough.