He comfortably won by a second and a half in 54.72 seconds to record his second best time ever.
The race showed he is regaining fitness nicely and he looks to break the 54 second barrier.
Father Jim threw a season’s best in a throws pentathlon competition in Sheffield to finish third.
The day started well with a hammer throw of 23.86m, followed up with a second best throw of the season in the shot putt with 8.78m.
But he threw a poor discuss of 23.63, before recovering with a season’s best javelin of 19.18m to put him back on course.
And another season's best in the heavy hammer of 9.29m saw Jim end up with a points score of 2033, which was another season's best by 50 points.