An intended runner at Doncaster on Sunday became the first horse to be refused entry to a British racecourse under coronavirus protocols.
Jam And Mam was set to make her debut for Lambourn trainer Archie Watson.
But one of the people accompanying the three-year-old filly to the races failed a temperature check.
Since British racing returned behind closed doors on 1 June, all attendees must pass a temperature check before they are admitted.
If anyone gives a confirmed reading above 37.8C, they will be refused entry as a raised temperature is a potential indicator of illness.
A British Horseracing Authority spokesman said: “Following arrival at the course, one of the members of staff travelling with Jam And Mam failed to meet the screening requirements to enter.
“In order to ensure that behind-closed-doors racing is as safe and secure an environment as possible for all attendees and minimise any risk of spreading Covid-19, those travelling with the horse were not able to enter the racecourse and as such the horse was declared a non-runner.
“This is in accordance with the protocols developed with organisations from across the racing industry, which are designed to safeguard the health of all those attending.”
Watson has not commented on the non-runner.