Perhaps the bonnet is already slightly ajar? Try pushing down on it to close it and then try pulling the lever again before attempting other methods. Worth a shot.
Hi,
Some feedback. I was able to open the bonnet by pressing down in it (over the badge) while someone else pulled the lever.
I also noticed the cable and springs on the catches in the bonnet has become slightly corroded. So I've sprayed some penetrating oil over the bits and hopefully is should loosen everything up.