The lunch which followed, at which the Princess, visiting as President of the British Olympic Association, talked with Legrelle and other shooters, amply made up for the slip. 'It will be a lovely story to tell my grandchildren,' said Legrelle, whose first name is Diane but who has been otherwise referred to since her father remarked on her rosy complexion as a new-born baby.
Things have been less than rosy for Legrelle here, however. When you are shooting well, nothing distracts you. When you are not, anything can. That the arrival of royalty affected her indicates which category the 40-year-old noblewoman has fallen into at her first Olympic Games.
Walking away from what proved to be her worst session of the competition yesterday morning, the countess mopped the sweat beading her brow and confessed that she felt like crying. Conditions at the Mollet del Valles range outside Barcelona were already brutal - the temperature was 88F and humidity 45 per cent - but it was her mental condition that was most distressing.
As she crouched with a Beretta 12-bore shotgun ready at her hip to track and blast the clay targets as they were slung into the air, she could feel a technique which had earned her a place as one of just six women in an Olympic field of 60 unravelling.
'Usually I like pressure,' she said. 'I use it. But I get the feeling here that I am just up against a brick wall. I lost concentration for that little fraction of a second just now and missed a whole pair of targets, which made me feel so upset that I missed another at the following stage.'
On the first day she had hit 69 of the 75 clays thrown up. Pretty good going? At this unforgiving level of competition it was only enough to leave her joint 52nd; and in scoring two fewer in yesterday's second part of the preliminary round she ended in 59th position. Second from last.
'Where has it been going wrong? If I knew that I would be a world champion,' she said, before waving brightly to a fellow shooter.
This is the time when all the possible reasons begin to tumble through the mind. With a sense of enquiry, rather than any desire to make excuses for herself, she runs through a few.
She had spent a lot of time making sure that her two sons, aged 10 and 14, back home in Jodoigne, near Liege, would be well catered for in her absence, although she conceded that the presence of two housekeepers was helpful in this matter.
Having lost three stones in three months prior to Barcelona through a course of diet and injections, she found that her gun no longer fitted as snugly at hip and cheek as it once had. Padding held in place by red masking tape which was becoming mis-shapen in the heat had clearly not presented the ideal solution.
She had not expected that much from an Olympic event which has not seen a woman medallist since it went mixed in 1968; and her low expectations were realised. 'What makes it even more discouraging is that the Chinese girl has come out and started to beat all the men,' she said, before adding with a rueful smile: 'And on top of it, she looks pretty.'
The Chinese girl was left sitting pretty too, as she went into today's semi-final in first place with a perfect two-day score of 150.
For Legrelle, some of the disappointment was tempered by the recollection of four years ago when, having qualified to represent Belgium, she had her place in the team withdrawn at two weeks' notice as it dawned on the selectors that she would not be shooting in an exclusively women's event.
But as she stared down at her broken and emptied gun, blackened with powder, it did seem an empty comfort. 'No,' she said. 'It doesn't feel right.'