He was “pretty tall and thin” when he joined Croydon Harriers, but now Martyn Rooney is standing tall as the skipper of the British Athletics squad at the IAAF World Championships.

The action gets under way in Beijing tomorrow (Saturday), with Rooney taking his place in the 400m heats on Sunday and the 4x400m relay on August 29.

Rooney, 28, is fifth in the men’s 400m British rankings and 14th in the world.

He started at Harriers aged 11, and coach Mike Fleet remembers the moment the European 400m champion first took to the track.

He said: “It’s fair to say you can see if young boys or girls have got potential and if they apply themselves they can do very well and Martyn looked promising.

"He was pretty tall and thin, which is always a good start.

“Like most lads he did several events, more so the 800m and cross country when he was young, but he moved onto the 400m and has progressed well ever since.”

Fleet also praised Rooney’s role at the club away from the track, as he keeps in contact with the young Harriers on Twitter, and attends the club’s formal dinners.

He said: “He’s great with other athletes, he’s very personable and he’s a great motivator.”

Rooney has good reason to look forward to competing at the Bird’s Nest stadium in Beijing over the coming week, as it was there that the Brit set his personal best of 44.60 seconds during the Olympics in 2008.

The sprinter then found success at the European Championships, winning bronze in the 400m individual and silver in the 400m relay in Berlin in 2010.

He then went one further four years later, winning gold in both the 400m individual and the 400m relay at the European championships in Zurich in 2014.