Historians may be interested in the following link /club_training_sessions/lunchtime-handicaps/ (scroll to the bottom), that I used to organise from KB on the second Thursday of every month.
In those days I was running a bit faster. My recollection is that the record was around 27 minutes but I can’t remember who held it.
The easy runners went round it in 66 minutes whilst the fasties did it twice in about 100 minutes. Gordon’s Strava here