Dennis rode the 13.8-kilometre opening individual time trial stage in 14 minutes and 56 seconds, clocking an average speed of 55.446kmh - Boardman's previous record was 55.2kmh set during the 7.2km prologue of the 1994 Tour in Lille.
The pan-flat course around Utrecht in the Netherlands was blessed with little wind, and despite the corner-strewn course provided the ideal platform for quick times.
Tour Down Under winner Dennis was the only rider to go under the 15-minute mark on the course, and established time trial legends Tony Martin (Etixx-QuickStep) and Fabian Cancellara (Trek Factory Racing) failed to beat his time.
In February, Dennis set an Hour Record of 52.491km - slower than his time trial speed, though of course over a much greater distance. Dennis later lost the Hour Record to first Alex Dowsett and then Bradley Wiggins.
Orica-GreenEdge holds the record for the fastest average speed in a Tour stage: 57.7kmh set during the 2013 team time trial.
The opening stage of the 2015 Tour is the only individual test against the clock this year, with only a team time trial on stage nine to break up the road stages. The 2015 race concludes on July 26 in Paris.
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