Can they charge me in these circumstances

This happend last night on the Totton ring the events are as follows. I went straight over a roundabout and had allready shot of down the dual carrige way a few people behind me turned off left at the round about hence not seeing Volvo T5 police car that was now behind me. Further up the road I noticed him slowed down all the proper manouvers etc, but he still pulled me over. This is where I need the help the police man was on his own! He asked me to sit in the back of the car so that he could show me the Vascar display ( A small black box with 2 digital displays and a few switchs on it) he explained that as I passed under a bridge the shadow cast by the bridge he used as a starting point and pressed a switch on the black box. He then sighted another point and as he passed pressed another switch, this he told me worked out my average speed over this distance which was 95 mph(not good). Question is can I be done for this offence being that there was only one officer in the vehicle there is no video evidence, Secondly how can this method be taken as accurate when the officer has to take one hand of the wheel to opperate the equipment, sight and mark a spot on the road at which to begin timing and doing all this while in commplete control of his vehicle. Anyone that knows a bit about this or is apolice man and can give away the trade secrets I would be very grate full as I know this will be 6 points and a big fine which won''t be good for the insurance. Keith Pickering superlight T7 KCP