Born in Croxley Green, Hertfordshire, Benning started his youth career as an amateur in the nearby area, with Watford Schools, Luton Town and Croxley Boys Club.
[1] Competing with full-time professionals for a place in the team, he did not make a single appearance under Neil McBain, the manager who signed him.
Benning had to wait until Ron Burgess's first game in charge on 14 February 1959 for his debut; a 3–2 defeat to York City at Vicarage Road.
[2] Benning became a regular first-team player for Watford in 1959–60, missing the club's second league game of the season and their sole fixture in the Southern Floodlit Cup; only Cliff Holton played more matches.
In his first season, he helped City win the league over their rivals Cambridge United.