Les McDowall became manager in 1950, and managed the Blues for more league seasons than any other manager. Known for his tactical awareness, McDowall's implementation of a system known as the Revie Plan resulted in two FA Cup final appearances, a defeat in 1955 and a victory in 1956. McDowall resigned following relegation in 1963, and his assistant George Poyser became manager. Poyser proved unsuited to the manager's role, and was sacked in 1965. Joe Mercer was appointed, and the club's golden era began. Mercer became the club's most successful manager in terms of trophies won, winning the League Championship, the FA Cup, the League Cup and the European Cup Winners' Cup in his six years at the helm. Over time Mercer's assistant Malcolm Allison sought a progressively larger say in non-coaching matters, and in October 1971 he took sole control of the first team, with Mercer becoming "general manager".