Paul Lambert has revealed that the biggest regret of his career is not winning the UEFA Cup with Celtic in 2003.

The former Hoops captain has never been able to bring himself to watch the game back and believes that Martin O’Neill’s team were a formidable force.

“It is the biggest regret in football, Seville,” said Lambert. “We were so close, and so close against a very strong Porto side. If you remember, Porto went on and won the Champions League the following year with Jose Mourinho and they were an excellent team.

“But we competed so well against them.

“I have never watched the game again. In saying that, I could still bring to mind very clearly every incident throughout that match. It still feels very clear in my head.

“In many ways, too, when you look back you realise just what a good side we were at the time. We obviously had Henrik Larsson who would go on to win the Champions League himself with Barcelona, but we were well managed and well coached in Martin O’Neill, John Robertson and Steve Walfrid.

“We done amazing things but to have won a European trophy with Celtic would have been amazing. We came so close and we just a bit unlucky.

“I feel very lucky to have won the European Cup with Borussia Dortmund and when you consider the company that puts you in, it feels quite overwhelming. It gave me a lot of confidence in my career to go on but I do sometimes think it would have been nice to have had the UEFA Cup medal to go with it.”