Shaw, who qualified for the 2018 World Ironman 70.3 Championships, had taken a year off from the sport but came back with a bang in Shropshire.
The 31-year-old, who is a Year 5/6 teacher and PE lead at Holy Cross Catholic Primary School, finished the 70.3 event in a personal best time of 4:02.33.
That was more than two minutes ahead of second-placed athlete George Martindale, with third-placed finisher, Dan Elliot, more than 10 minutes behind.
“It’s been a long time but I’m back doing triathlon,” said Shaw. “I’ve been training for the last five months and I’m fitter and faster than before.”
Shaw was grateful to Alltrax Cycles in Wembley who got his bike ready for the event at Alderford Lake in Whitchurch, Shropshire.