The wire breaks and you cannot open to access the engine
Get a regular steel wire and attatch it ti the locking arm for the bonnet. Then just let it run where it does not disturb anything. I have my emergency wire as in the photo. At the brake reservoir I have a loop. The bonnet is very flexible and easy to raise enough to let your finger grab the wire. Just pull a bit and the bonnet will open.
A piece of cake. Don't make things too complicated.
Here's how I opened a bonnet on a 1750 GTV. Use a piece of wood and a cloth, the latter to protect the paint. Raise the bonnet at the edge, it is very flexible and easy to raise.
Then raise the hood so you can see through, use a torch so you can see the mechanism.
I used a hook made from an alloy stick. Anything will do. The basic princip of how I did it.