Wilsmore, who also runs for Bristol & West, clocked three minutes and 52.12 seconds in the final of the championships at Lee Valley. He won by nearly three seconds, with Chiltern’s James McCarthy second in 3:55.25.
Wilsmore had previously eased through the heats with a time of 4:06.77.
The weekend before in Cardiff, Wilsmore had won the same event at Cardiff Met’s New Year Open Indoor Meet in 3:48.86, which was his fastest competitive time over 1,500m for nearly four years.
City of Plymouth’s Paralympic hopeful James Arnott also showed good early season form at the South of England Championships at Lee Valley.
Arnott set a new 60m personal best of 7.31 seconds to finish third in his under-20 heat. Last year, Arnott had set a PB in the same competition of 7.47.
Fellow City of Plymouth athlete Dean Smith clocked 1:59.08 in the 800m heats at Lee Valley.