The Hess mission is still hotly debated and there is no conclusive evidence that the mission was officially authorized. Anyone who says that Hess was there to negotiate peace on behalf of Hitler is operating on pure speculation. We won't know until the UK releases the classified information on it, which they have repeatedly failed to do. It is equally likely that Hess was just exhibiting the early stages of the psychiatric disorder that later became full-blown.

It may be worth mentioning that a peace-feeler was made via Mussolini (neutral at the time) during the leadup to the Dunkirk crisis. It got nowhere, as the successful evacuation gave Churchill's government enough strength to remain in power.