3pm update: A statement from Transport for London confirms that the bus initially stopped on the M1 because the hybrid battery, which isn't designed for long-distance non-stopping journeys, was losing charge. Once the battery had re-charged, the driver was unable to re-start the vehicle due to it having run out of diesel. We'd love to hear the phone conversation between TfL and Arriva, the bus operator, this afternoon...
12.50pm update: The BBC's Tom Edwards reports that the vehicle had in fact ran out of diesel, and that the driver had also seen a warning light on the braking system. The tow truck was called as a precaution.
Unveiled in Trafalgar Square on Friday, it seems the New Bus for London might be experiencing some technical trouble already.
LBC has a pair of photographs depicting the stricken vehicle on the hard shoulder of the M1, near Dunstable, whilst en route to the testing centre at Millbrook. Transport for London have insisted that the bus was taking a scheduled rest stop, on account of its hybrid engine not being designed to drive for long distances. However, a second photograph, showing a tow truck parked up in front of the bus, renders that explanation somewhat implausible.
Should the ticker trouble be resolved, the New Bus is scheduled to be shown off at various points around London in January; there's a complete list on the TfL website. It will be put into service on the 38 route on 20th February 2012.