I represent the Queen ...

In my former life at the European Commission sometimes you signed or agreed to a contract given to some dodgy academic or consultant. The wording of the contract was at least as dodgy as the academics or consultants who won it, something like "due to the delegated power from the Treaty to the European Commission to enact ... blablabla ...."

Here in New Zealand things are crystal clear: The words in the contract start with "I, on behalf of the Queen, agree to give a contract to ...."