At the weekly 5k event new to Clair Park, Haywards Heath he was the first of 85 runners with a time of 18.05.
There was a classy field of local talent andMullen was delighted to come out on top.
Kat Barrett was 14th in 22.50 a new PB. Mike Essex clocked 24.07 on his first attempt, there was 27.16 for Graham Kenward and a new PB, while young Harrier Josh Essex completed his first run in 29.33.
There were also first-time runs from Irene Parsley 33.06 and Abgail Redd 33.23.
This joint initiative between the Harriers and Burgess Hill Runners is free to enter and is one of several events in Sussex which are perfect for new runners to get involved with - just check out www.parkrun.org.uk to register and find out more.
Over at Tilgate parkrun, Jack Chivers was 12th for a new PB of 19.42 and Natalie Chivers also was at her best in 26.30.
Down at Preston parkrun, Terry Bryan clocked 26.22 on his debut.
The Harriers contributed 14 runners to The Highdown Hike organised by Worthing Striders as part of the West Sussex Fun Run League. The annual summer race always takes place during the evening of the first Wednesday in August.
This year’s race last week was a two-lap 4-mile cross country run on Highdown Hill, Worthing. As the name suggests, the course is undulating throughout and is run on a mix of paths and tracks.
Tom Mullen took a brilliant sixth place with 24.55 in this quality field of 357 runners.
There were great runs from Phil Payne in an excellent 13th position with 26.02, 30th was Tim Hicks 27.40, and Barry Tullett recorded 27.45.
New lady member Izzy Coomber caused much excitement with her fine debut for the club in a terrific 27.56, while Mike Essex clocked 32.04, Steve Horn 35.52, 38.46 Richard Bates 38.46, Michelle Pearce 39.35, John Gill 40.53, Justine Denyer 43.09, Michele Holdstock 45.36 and Jenny Denyer 50.56.
The U15 Harriers Track and Field team took part in a league event in Horsham on Friday.
Both the boys and girls teams came fourth but were each weakened by summer holidays.
Standout performances came from Anna Hamilton, who was 2nd in 100m with 15.3 B string, as well as 2nd in the shot with 4m74; Christian Lambert 2nd in the B string discus 20m21 and javelin 17m50; Dan McKay was a great 2nd in A string javelin with a solid 20m81.
Harrier Andrew Biggs bravely entered the Bewl Olympic distance Triathlon on Sunday, a 1500m swim, 40km bike and 10 km run.
He finished 78th in a great time of 2hrs 33mins 57secs and afterwards said: “The course was harder than I expected especially the run, the 4 laps of running included up a hill which was roughly 1km each time.
“It was a really tough 10k, as it took me 48 mins.”
Fellow Harrier Kat Barrett reported her run was very painful, “I would say mine was sheer torture!,” she said. “But I was delighted to complete this challenging event.”
Barrett competed in the sprint version at Bewl, which is half the Olympic distance, but unfortunately currently she has no confirmed position or time as she was given the wrong chip number.
But Kat she believes she came 6th and her time would have been around 1 hr 22 mins.