Yes. Fuels you purchased four years ago has almost certainly been consumed so no claim on that, anything you’ve already incorporated in jobs that you’ve finished/invoiced before you registered then no claim on those either.
Basically if you could go out and see it in your yard / van / hand on the day your VAT registration began/begins then you can claim for it otherwise you can’t. Also as I said before if you bought a bulk of 500 bricks for say £500 plus £100 of VAT then if on that day you’ve only got 100 (1/5) of them left then you’d only be able to claim £20 (1/5) of the VAT you we’re charged for them.