The Coventry City striker-turned-midfielder, who failed to make the grade at Arsenal, took full advantage of his first senior start by putting in a busy display on the Irish right and scoring the winning goal after 26 minutes.

Barrett’s career has been slow to get going, but then it is not easy trying to force your way into a squad that already contains the world-class talent of Thierry Henry, Dennis Bergkamp, Robert Pires and Co.

A loan spell at Highfield Road turned into a permanent move and his international career was limited to becoming the most-capped player and record goalscorer at under-21 level, plus two substitute appearances for the senior team – although he did mark his debut nearly two years ago with a goal against Finland.

However, the Unity Cup – which was not exactly something the Boys in Green had been looking forward to – altered 22-year-old Barrett’s international statistics for the better.

He came off the bench to earn his third cap in Saturday’s 3-0 defeat at the hands of Nigeria and then grabbed a well-struck winner to see off Jamaica at The Valley.

With Nigeria having already lifted the trophy, Kerr kept his promise to give his fringe players a chance. In fielding Ireland’s most inexperienced line-up for several years, he made seven changes to the team which started on Saturday, including giving a full debut to Sheffield United goalkeeper Paddy Kenny.

There was also an introduction to international football for Celtic prodigy Aidan McGeady, who came on for the final eight minutes for his first cap.

The raw recruits were not tested too much by the Reggae Boyz and Birmingham striker Clinton Morrison had two glorious chances inside the opening 16 minutes to add to his tally of five international goals on what was his 20th appearance for his country.

After eight minutes he was unmarked at the back of the six-yard box when Barrett headed the ball over stranded Jamaica goalkeeper Donovan Ricketts from the right channel.

However, it was a poor effort on an unguarded goal as he sent his header against the underside of the bar and the ball was hooked clear.

Eight minutes later Morrison stole a yard on the Jamaican defence as he charged down the left, but he carried the ball too wide and from the edge of the six-yard box he drove straight at the goalkeeper.

It was left to Barrett to create a chance out of nothing when he gave himself a bit of space and fired home a low drive.

The Irish do not score bundles of goals, so a goalscoring midfielder in the ranks will give Kerr something to think about ahead of the World Cup qualifying campaign which begins in September - although it will probably take a number of injuries or suspensions to give the youngster a realistic chance of featuring.

The lowest crowd of the three matches, just over 6,000, made plenty of noise but were not treated to any decent goalmouth action in the second half.

In fact, the loudest cheer was reserved for a 66th-minute male streaker on a balmy night in south London.

The Irish squad flies out to Amsterdam tomorrow for a friendly against Holland on Saturday.

Kerr will bring back the experienced campaigners for what on paper, at least, promises to be an attractive friendly.