The on-loan Nottingham Forest striker covered the 10-mile course around Portsmouth in one hour 11 minutes and 33 seconds in his first tilt at distance running.
“I’m really feeling it today – I’m not built for running 10 miles,” he told us.
“I wanted to beat one hour 15 minutes and was really pleased with my time.
“It was hard work but thousands of people came out to support the runners and they were a massive help.
“I’ve raised more than £1,400 on my Just Giving page and the lads at Forest had a whip round and contributed £1,000.
“I can’t thank everyone who donated enough – the run was tough but I was determined to get through it. I just hope training isn’t too hard tomorrow because I’m as stiff as a board.”
Billy and his partner Jade set-up the LJS Foundation in memory of their son Luey, who passed away aged just two days old after being born with gastroschisis, a defect that causes a rupture of the abdominal wall, which exposes the intestines.
Saturday marked the first anniversary of Luey’s birth and Forest fans paid tribute to him by chanting Billy’s name for 60 seconds in the 24th minute – which represents his squad number.
There were similar scenes at Doncaster’s game against Notts County and Southampton’s clash with Spurs yesterday.
Billy added: “It has been an emotional weekend but doing the run took my mind off things.
“Football fans get a lot of bad press but the support they have given me and my family is overwhelming. I would like to thank them all.”
Supporters can lend their support to the Foundation by purchasing LJS wristbands from the Forest Megastore, priced £3.