Oh! and by the way it passed the MOT. It may be a comfort to future owners to know that a spike on the speedo is quite a common thing.
A BIG thanks to all that have taken this journey with me and given me some valuable input.....
Rob...
Following this post, I have tended to keep an eye on my speedo when starting and surprise, surprise on just one occasion last week, it flipped up to 50mph. Hasn’t done it since and I have done no electrical mods on the car. So that seems to back up the theory “they all do that” (sometimes)