Usain Bolt’s withdrawal from the 200m meant it was the men’s 400m which took centre stage, with Merritt expected to show his dominance just a week before the start of the Olympics.
However Diamond League leader Merritt pulled up with a hamstring injury and did not finish, although afterwards the American allayed fears by claiming it was just a twinge.
The race saw a season’s best from Jonathan Borlee as the Belgian held off James Kirani of Grenada, beating the World Championship gold medallist by two hundredths of a second with 44.74 seconds.
In the shock of the night, two-time Olympic pole vault champion Yelena Isinbayeva did not attempt a height until 4.70m, before failing three times. Britain’s national record holder Holly Bleasdale cleared 4.45m and 4.62m before bowing out at 4.76m. Silke Spiegelburg won the event after clearing 4.70m.
Chris Tomlinson finished third in the long jump and Britain’s Robbie Grabarz second in the high jump.