The pain began before Tower Bridge. By mile 15 Shane Williams’ glutes and hamstrings were pleading for mercy.
As he left the City and passed along the Embankment his head started to throb. His shoulders cramped up. Finally, his calf went.
Yet when Wales’ record try scorer had finished the London Marathon and caught his breath he paused and thought to himself, ‘how good was that’!
“Worth every second of the pain,” said the wing wizard. “Loved every moment. It gave me the feeling back again.”
It is a decade since Williams’ last Test, seven years since he announced his retirement from playing.
He might have thrived in the land of rugby giants but this pocket rocket makes no such claim about life beyond the final whistle.
“I knew there was going to be a big void in my life once rugby had gone,” he said. “Not playing was something I absolutely dreaded.
“It’s the camaraderie of the day to day stuff you miss the most. I struggled without it, I really did.”
Williams was luckier than most. He saw it coming. He started to prepare whilst still running rings round opponents.
Before the last of his 58 Wales tries he started putting in place charity challenges, be they Ironman, marathon, gruelling bike rides.
“People always think ‘you played rugby or football, you earned quite a bit of money, you did quite well, you must be fine’,” he said. “But everyone has their problems. Money doesn’t solve everything, I can assure you.
“We all cry, whether we’re a 6’11 second row or a 5’6 winger that used to play for Wales. We all get upset, depressed, suffer from anxiety in some shape or form.”
Last weekend brought Mental Health Day and a reminder that, as Williams puts it, “life’s not all sunshine and rainbows.”
He reckons retiring from professional sport must be like coming out of the military, going from a team environment to suddenly out on your own and a bit lost.
“You go from spending almost every day – breakfast, lunch, sometimes dinner – with these boys around you,” he said. “Then one day they’re not there any more. It can be very, very lonely.
“I’ve spoken to a lot of lads that have really struggled and at times been in dark places. Some are still struggling five to 10 years after retiring. As a sport we need to look out for each other more.”
Williams’ marathon effort brought a personal best time of three hours 24 minutes and raised funds for the magnificent Velindre Cancer Centre.
From there he quickly turned his attention to supporting the Tackle HIV campaign led by his great pal Gareth Thomas.
“I know people are going to say I’m having a mid-life crisis!” Williams laughed. “But challenging myself, getting that competitive feeling again, makes me feel alive. Long may it continue.”
Tackle HIV is a campaign led by Gareth Thomas, in partnership with ViiV Healthcare and the Terrence Higgins Trust to tackle stigma and misunderstanding around HIV. For more information visit www.tacklehiv.org and follow @TackleHIV