They’re not very high (1.35m) or wide (1.4m). A side-to-side jump took a few practices over the bonnet to get the run-up right, then it was plain sailing over the roof.
A more notable achievement was that I could get into the boot (trunk) of a Mini. This was particularly useful as the attendants at Adelaide drive-in movie theatres never bothered to check for stowaways in the boots of Minis. I got a few free movies from that.
I doubt that I could jump over a BMW Mini but I’m sure I could fit into the boot.