Whether or not that is true in law (and I'm shocked if it is true), it does not always work like that in practice, fortunately.
...
When I had a legit claim of serious shoulder injury the insurers claimed it was only serious due to a pre-existing medical condition, and the injury received was simply a repeat of a previous injury. They wanted to reduce damages severely, if not completely.
As it was my doctor notes simply stated "pain in shoulder" (following being knocked off my bike
). The previous injuries were very very minor - I recall getting one 50p sized bruise and having stiffness for a couple of days (oooo errr missus). Had it not been for the fact I was collecting a prescription for Mrs Nutty I wouldn't have bothered seeing the doctor. As it was I asked if they had a free appointment for the morning if I woke up in pain, and they said that the doctor was free and I might as well walk straight in.
I managed to get the claim of reduced damages thrown out by getting the doctor to confirm the shoulder referred to in the notes was the right shoulder, whereas this claim was for the left.
I rarely went down the doctors prior to that, but am now very reluctant to go in case anything goes on my notes that I may regret at a later date.
I know the standard advice on here post any accident is to get the injuries documented, but for myself I'll only get the injuries documented if they're major enough that the nice men in white coats carted me off to A&E.