I mean, he may not be a regular at matches, but I don't think he'd make it up to look popular:
https://www.bbc.co.uk/sport/av/football/30342970
"The former British number and four-time Wimbledon semi-finalist is a lifelong Oxford United fan, and displayed his own football prowess during this summer's World Cup Copa-uppy challenge -
managing an impressive 92 keepy-uppies with a tennis ball."
https://www.theguardian.com/sport/2009/jun/19/tim-henman-small-talk-interview
"I'm Oxford United."
https://www.bbc.co.uk/oxford/features/famous_oxfordshire/tim_henman.shtml
"Away from tennis Tim supports Oxford United Football Club."
https://www.atptour.com/en/players/tim-henman/h336/bio
"As a youth, Henman played football (supports Oxford United Football Club)"
https://www.standard.co.uk/sport/henman-don-t-call-me-tiger-6340623.html
"He does follow England's football fortunes, finding time during the French Open to visit a British pub in Paris showing a live match, and he looks out for the results of Oxford United, his home-town team, although his father is more of a fan.
Henman lives in Barnes but shows no signs of joining the Fulham bandwagon despite their magnificent form in Division One under Jean Tigana - "I only know one of their players and who owns the club!"
Etc, etc over many years. I'm not sure why people are keen to deny it but I think we should just accept that Tim Henman is, to whatever extent, a Yellow.