The fifth run of the show, which stars Dennis Waterman and Amanda Redman, opened to an average of 8.7m (37%) between 9pm and 10pm last night, according to early viewing figures.
The figure is an improvement on already strong ratings for the fourth series debut, which was seen by 7.6m in an identical slot in April last year. The 2006 opener, also at 9pm on a Monday, drew 7.2m (28.4%).
ITV1 failed to achieve even half of its rival's audience in the 9pm hour, with Police, Camera, Action! on 4.1m (17.5%). The channel's only rated more highly last night with Coronation Street, with 8.5m (43%) and 8.4m (37.3%) for its 7.30pm and 8.30pm episodes respectively.
BBC Two's retail show Mary, Queen Of Shops interested 1.9m (8.2%) in the slot and Banged Up, the new Five series in which David Blunkett attempts to teach delinquents the error of their ways, was seen by 918,000 (3.9%).
Channel 4 interested 1.1m (4.7%) in the 9pm hour with 7/7: The Miracle of Carriage 346, marking the third anniversary of the attacks, while its largest audience of the night was 3m (16.8%) for Big Brother from 10pm.