Britain has been tied to Prussia's major rival Austria by the Anglo-Austrian alliance since 1731; Prussia has been allied to Britain's enemy France.

Following the War of the Austrian Succession, during which she has lost the valuable province of Silesia, the Austrian Empress Maria Theresa had tried to gain British support for a proposed military action to reclaim it.

The results of the War of Austrian Succession are clear, however: Britain no longer views Austria as powerful enough to check French power but is content to build up smaller states like Prussia.

When the British government refused, the Empress had become disenchanted with them—and in 1756 makes an alliance with France.

The British, suddenly without a major ally in continental Europe, hastily conclude a similar pact with Frederick II of Prussia, who is receiving reports of the clashes in North America.

Both signatories hope the alliance will forestall a major European war by maintaining the European Balance of Power.

Prussia has a number of leading British supporters including William Pitt.

The Convention of Westminster, a treaty of neutrality, is signed on January 16, 1756, between Frederick II and King George II.

British fears of French attacks on Hanover, the family seat of the British monarch under his title as the duke of Brunswick-Lüneburg, had been responsible for the development of the treaty.

Based on the terms of the agreement, both Prussia and Britain will prevent any other foreign power passage through Germany, and that Britain will not aid Austria in a renewed conflict for Silesia if Prussia agrees to protect Hanover from France.

Protection of Hanover is important to Britain because it is a possession of its king.

Britain feels that with Prussia's growing strength, it will be more able to defend Hanover than Austria.

The Westminster Convention and the resultant Anglo-Prussian alliance are part of the so-called Diplomatic Revolution.