Defender tdci speedo problems

Hi all,
I have a problem with my speedo. It will cut out half way through a drive to work. It sometimes it comes back on sometimes. There doesnt seem to be a pattern or anything like that. The rest of the dash is fine. The milage counter stops so im thinking the speed sensor is on its way out or there is a loose connection. Before i start ripping things apart. Does anyone have any suggestions?

Hello