In the women’s event, Backstedt started third from last and set the time to beat as she came home 5.43secs quicker than Germany’s Franziska Koch, who eventually finished third.
She told reporters that she started to dream of winning after making a storming start: “In the first half, when I heard the first time check, I was thinking ‘OK, maybe it’s possible’.
“But I knew also that Marlen was super strong and that she has a very big engine.
“So I knew that it was possible that she would bring a lot of time back on me and she did, so massive respect to her.”
Reusser, the final rider to start, was more than 10 seconds behind Backstedt at the first checkpoint but paced her effort brilliantly on the 39.2km course, which was almost double the usual length, to claim a second time-trial gold medal to add to last year’s victory in Rwanda.
The Swiss star, who has also won two world silvers and a bronze in the discipline, was the form rider going into the championships.
The four-time European champion had been virtually unbeatable at the discipline this year, having won time-trial stages at the Tour de France Femmes and Giro d’Italia Women.
But Backstedt made her battle hard on a long, winding, technical course to secure just the third British medal in the discipline, with Emma Pooley taking gold in 2010 and bronze a year later.
She added: “My main thing was ‘don’t go out too hard, don’t go out like it was a 22km time trial, go out like it was a 40km time trial and if you have got anything left in the final then give it everything that you have got’.”