Shannon was born in Liverpool; a centre-forward, he started his playing career with his hometown club of Liverpool in November 1944. He made his debut for the Reds four years later, against Manchester City at Anfield on April 17, 1948, as a substitute for Albert Stubbins. His only goal for the Merseyside club came the following season, in a 2-1 win at Sheffield United on August 30, 1948.
After Shannon's contract with Liverpool expired in November 1949, he joined Burnley. Playing on both flanks for the Clarets, Shannon clocked up 281 league appearances and scored 44 goals.
Shannon retired from playing first-team football in September 1958, when he played his last game at the age of 32, a 2-2 home draw against Luton. He then captained Burnley's reserve team for a year.
Coaching and management
In 1959, Shannon moved into coaching with Everton and, in 1962, he joined Billy Wright's backroom staff at Arsenal.
After four years at Highbury, Shannon took over as manager of Second Division Bury. The Shakers finished bottom in his first season in charge, but he guided them back the following season only to see them make the drop again in 1969.
After Bury's relegation, Shannon took over as manager of Blackpool, with whom he had instant success, winning promotion back to the top flight. In 1970/71, however, his yo-yo effect reared its head again, when the Seasiders finished bottom and were relegated to the league's second tier once again. Shannon had left his position only two months into the season after only seventeen months in charge; he was replaced, in a caretaker role, by Jimmy Meadows.
Shannon then moved to Greece and coached PAOK FC from 1971 to 1974. He led the Thessaloniki outfit to victory in the Greek Football Cup twice in 1972 and 1974, narrowly missing the league title in 1972. The team he created, however, centered around the talents of Giorgos Koudas, Stavros Sarafis, Christos Terzanidis and others, did win the championship in 1976, breaking a 30-year monopoly by AEK, Olympiakos and Panathinaikos.
Shannon then coached Iraklis in 1975 - 1976, again winning the Greek Cup. Afterwards, he coached Olympiakos (1976 - 1977), OFI Crete (1978 - 1980 and 1982 - 1984), Ethnikos Piraeus and Aegaleo FC (1985).
After his stint in Greece, Shannon became a scout for Luton, which would be his final role in football.
His knowledge of football led to his being enlisted as an advisor on the Channel 4 series The Manageress.