Gabriela Szabo of Romania won gold

O'Sullivan, who returned to top class competition this year after the birth of her daughter, gave it everything on the final lap to overtake her rival whom she beat at the Europeans in Budapest two years ago when she completed an historic 5000m/10000m double.

But Szabo would not be denied as she fought off every attack by O'Sullivan to win in 14:40.79 seconds, slashing 19 seconds off the Games record set by Wang Junxia of China in Atlanta in 1996.

O'Sullivan finished in 14:41.02 with Ethiopia's Geta Wami third in 14:42.23. Pavey clocked 14:58.27 on her Olympic debut, having missed two years of competition through injury.

Torrid pace

O'Sullivan was relieved she had been able to keep up the torrid pace, saying: "There were definitely times when I could of got caught up in the middle of the field.

"I'm just so happy that I hung in there, got back on the pace and got back in the race again.

Britain's Jo Pavey ran her best time

"I guess I felt like I belonged there once I got into it but there was some kind of time when I had no control over it and the race was very nearly taken out of my hands."

It appeared O'Sullivan might finally take the lead against Szabo coming down the final straight, but she was unable to find a burst that would carry her past the Romanian.

"I was going as hard as I possibly could and I was trying and trying and trying," she said.

O'Sullivan indicated she could well try to go one better in the 10,000 metres.

Come back

"I felt half guilty doing a lap of honour but there were so many Irish fans and Irish flags in the stadium I felt I had to show my appreciation so I went round the track.

"I would love to come back and go round again," she said.

"It was nearly a dream come true. In some ways it is because I am going to get a medal round my neck and represent everybody in Ireland.

"I don't know whether to laugh or cry. I am caught in between really.

"I am happy with a silver - I think."