Field Marshal John Colborne, 1st Baron Seaton, was a British Army officer and colonial governor. After taking part as a junior officer in the Anglo-Russian invasion of Holland, Sir Ralph Abercromby's expedition to Egypt and then the War of the Third Coalition, he served as military secretary to Sir John Moore at the Battle of Corunna. He then commanded the 2nd Battalion of the 66th Regiment of Foot and, later, the 52nd Regiment of Foot at many of the battles of the Peninsular War. At the Battle of Waterloo, Colborne on his own initiative brought the 52nd Regiment of Foot forward, took up a flanking position in relation to the French Imperial Guard and then, after firing repeated volleys into their flank, charged at the Guard so driving them back in disorder.

Field marshal (FM) has been the highest rank in the British Army since 1736. A five-star rank with NATO code OF-10, it is equivalent to an Admiral of the Fleet in the Royal Navy or a Marshal of the Royal Air Force in the Royal Air Force (RAF). A Field Marshal's insignia consists of two crossed batons surrounded by yellow leaves below the Tudor Crown. Like Marshals of the Royal Air Force and Admirals of the Fleet, Field Marshals traditionally remain officers for life, though on half-pay when not in an appointment or retired. The rank has been used sporadically throughout its history, and was vacant during parts of the 18th and 19th centuries. After the Second World War, it became standard practice to appoint the Chief of the Imperial General Staff to the rank on his last day in the post. Army officers occupying the post of Chief of the Defence Staff, the professional head of all the British Armed Forces, were usually promoted to the rank upon their appointment.