The 21-year-old from Lincoln was ranked only sixth in the world and qualified sixth for the final but once he got there he upset the form completely. Indeed, during the last 100 metres, there was even a hint he might get the gold but he was beaten at the finish by New Zealand's Danyon Loader.
Palmer was never out of the medal positions from the start. At 100 and 200 metres he was third but as Daniel Kowalski faded, he got stronger, touching just behind Loader, who also won the 200m free. He was ahead briefly but could not sustain a ferocious pace, clocking 3:49.00. The winning time was 3:47.97.
Palmer's first thought was to his house which was burgled the last time he was at a major competion, the European Championships in Vienna last year. "To anyone listening," he said, "my mother and father are here but my brother and sister are looking after my home. That's for anyone thinking of doing it over while I'm here.
"I've never been as nervous as I was before that race," he added. "I just got in and gave it everything I could. I didn't have that much left on the last length but a silver medal, you can't complain.
"Straight away it felt so different from this morning [in the heats], it felt so comfortable. I wasn't kicking at all. I got to 100 and had a look around and saw only another couple of other guys with me and I started to think, yes you can do this.
"I just carried on trying and trying. Danyon went away from me at one of the turns, but it worked so well in the end. I've worked and worked for this. I couldn't tell you how much work I've done."
When told it was the first medal Britain had achieved in the Games, Palmer added: "I couldn't care if it's the last medal. I've got a medal that's all I'm bothered about."
Palmer has been used as a guinea pig in training with a device that issues a metronomic note to guide the pace of his stroke. "I would like to thank Patrick Miley who invented it. It certainly contributed to the silver. It's hard to describe how I'm feeling. I know second is not as good as first but at the moment it feels great. My best is yet to come in four years' time in Sydney."
Palmer apart there has been little to set red, white and blue pulses racing but if they were giving out gongs for the most underwhelming performance of them all then the men in the 100m backstroke yesterday would be among the leading contenders.
In Neil Willey and Martin Harris Britain had the third and sixth fastest men in the world this year yet those performances looked misleading one- offs when they failed to reach the final by a margin as big as the question mark over the team's preparation.
Willey, a silver medallist in the World Short Course Championships last year, finished a dismal fifth in his heat with a time of 56.27sec that was more than a second slower than his personal best. Harris, the British record holder, was even worse with 57.17 and finished 26th overall.
"I don't know what was wrong," Willey said. "I wasn't ready mentally or physically. I will have to sit down with my coach and work it out."
The male backstroke swimmers were not alone in their disapppointment. Caroline Foot was more than a second outside her best with 1:03.04 in the 100m butterfly while Marie Hardiman finished sixth in her heat for the women's 200m breaststroke.
South Africa's Penelope Heynes, meanwhile, is cutting through records. Having set a world mark for the 100 metres breaststroke on Sunday, she added an Olympic record with for the 200m breaststroke with 2.26.63 before going on to take the gold medal in the evening's final.