Allen followed in his father's footsteps when he was appointed manager of the Robins in September 2008 but, after a difficult spell, left by mutual consent in December 2009.
Two stints at Barnet followed, sandwiching a short reign at Notts County, before Allen took over at Priestfield last summer. And he has enjoyed a season to remember in Kent, clinching automatic promotion with last weekend's 1-0 victory over Torquay.
The Gills could potentially seal the League Two title at Whaddon Road when the two teams meet on Saturday but Allen insists he is not going there to exact any kind of revenge on the Gloucestershire outfit.
He told Gillingham's official website: "No scores, I don't have to settle scores with anybody. I just do my job; I don't live in the past, I live to the future. It's a fantastic football club and it's the club I supported as a little boy, and for several years when my dad was the manager the supporters were good to me.
"I have some great memories there from when I was a boy, great times and I will always be very fond of that football club and no-one will ever change that.
"I'm going back there now as the manager of Gillingham. I certainly won't be dancing around on the touchline, I'll show respect to their supporters.
"I didn't do a very good job there, I made a lot of errors and a lot of mistakes and I should have done things differently."