Former Welsh international forward John Hartson joined Norwich City on loan from West Bromwich Albion on 12th October 2007 for a month's loan. He made his debut the following week in the 3-1 home defeat to Bristol City

His career began in 1992 as a trainee at Luton Town, and went on to play for Arsenal, joining in January 1995 for £2.5 million uner George Graham's managership. With the signing of Dennis Bergkamp, who was preferred up front to partner Ian Wright, Hartson featured less under Graham's successors Bruce Rioch and Arsène Wenger. In February 1997 he was sold to West Ham United for £3.2 million

For West Ham, Hartson scored 33 goals in 73 league and cup appearances for the East London club. There was a training ground incident when Hartson was playing for West Ham in 1998, where he kicked Eyal Berkovic in the head while in front of television cameras. No charges were brought forward, and Hartson has admitted in his biography that this was an error of judgement.

He has since played for Wimbledon and Coventry City,[1] before a £6m transfer to Celtic allowed him to thrive in the Scottish Premier League

On 26 June 2006, Hartson signed a two-year contract with English Football League Championship side West Bromwich Albion in a £500,000 move. Hartson scored twice on his Albion debut in a 2-0 Hawthorns win against Hull City on 5 August, 2006.

Hartson holds 50 first team caps for Wales. He retired from international football in early 2006 but in August that year he stated that he would come out of retirement to play if John Toshack needed him. He is currently the 9th top scorer of all time for the international team.

New Norwich manager Glenn Roeder quickly returned Hartson to West Brom.

On 21st November 2007, Hartson turned down an audacious attempt by Chester City to sign the former Wales international, 32, on loan with a view to the move being made permanent in January but Chester chief executive Bob Gray told the Wrexham and Flintshire Evening Leader: "The player won't drop down to play in League Two."

The Baggies released Hartson from his contract on 30th January 2008. He had made 24 appearances for them, scoring six times. On 7th February, Hartson announced his retirement citing problems with weight and fitness as the reasons. His four games for Norwich brought his career total to 399 league games.

On 3rd March 2008, Scottish minnows East Stirlingshire launched an ambitious approach to make Hartson their next manager following the departure of Gordon Wylde. Shire owner Spencer Fearn said: "John is really keen and we had a great chat. He's going back to Swansea and we'll know on Tuesday if he's taken the job. This could be a big move for us and his first step into management." East Stirlingshire were second bottom of the Scottish Third Division as the story broke and were seeking to avoid a sixth successive bottom-place finish.

In July 2009, John was diagnosed with testicular cancer. The cancer was also reported to have spread to his brain and lungs.He has received treatment at Morriston Hospital in Swansea.

He then established himself as a regular pundit for the BBC and BT Sport.

On 26th August 2017, Hartson joined Livingston to help coach their strikers one or two days a week. He applied for the vacant managerial position at Livingston in the summer of 2018, following David Hopkin's resignation on 30th May 2018..