Four-time Olympic gold medallist Sir Chris Hoy has pulled out of track cycling's European Championships.
The 35-year-old Scot withdrew with a chest infection as Saturday's individual sprint began and is very unlikely to compete in Sunday's keirin.
"Chris got up not feeling well. He was dizzy in the warm-up and after a doctor's exam we decided to withdraw him," said GB coach Shane Sutton.
"He'll be disappointed - he was looking forward to the run-out here."
Hoy finished a lowly fifth in Friday's team sprint alongside team-mates Jason Kenny and Matt Crampton after Kenny's wheel slipped at the start of their qualifying run.
At the time he gave no hint of his condition - "on the plus side my lap was quick, so all I can do is focus on tomorrow," he wrote on Facebook - but Sutton confirmed Hoy has had the infection for some time.
"The doctor says he's wheezing quite a lot and has blocked sinuses," said Sutton.
"He's had this lingering for about a week but he went quite deep yesterday, in the team sprint, and that one effort probably pushed him over the edge.
"It's best for him to stop now, go home, recuperate and get ready for [the next World Cup race in] Kazakhstan."
Hoy will miss out on Olympic qualification points that had been on offer at the Euros, in the Dutch town of Apeldoorn, but Britain is so well-placed in the Olympic rankings that his withdrawal here will have no impact on GB's Olympic fortunes.
Even suffering illness, Hoy had qualified fourth-fastest in the individual sprint in Saturday's opening session before deciding to withdraw.
Kenny, sixth-fastest in qualifying, will fly the flag for Great Britain in the men's sprint competition having reached the semi-finals.
Team-mates Victoria Pendleton and Jess Varnish were both eliminated from the women's individual sprint, Varnish exiting in the last 16 before Ukraine's Lyubov Shulika defeated Pendleton in a best-of-three quarter-final.