Op is rude. Granted. But
surely a delivery man instructed to deliver a letter can't jump a fence to do so. The letter wasn't serving docs as per court requirements, it was delivery of a letter. Why didn't the lawyer use Aus Post?
Surely if you have a gate, a no trespass sign, some random person sent by a lawyer to deliver a non-court required item can't just jump the fence. He wasn't an a auspost worker, nor law inforcement nor utility meter reader.
I would try take the lawyer to vcat for damages.