I have no recent experience of this, but I received a small payout as a minor following involvement in a car crash that was invested for more than 10 years in the same scenario. It was worth almost exactly the same as when it went in when I got it - perhaps ten or twenty quid more. I had been told that by the solicitor, I think - whatever way they invest them, its to guarantee they don't lose value so in reality barely any increase is usually seen. As I say, that's a very out of date experience - I received my payout in the early 2000s - but I would be surprised if their approach to investment had changed in the intervening period.