Davy Russell will miss the Grand National meeting at Aintree after failing to gain medical clearance from the British Horseracing Authority as a result of the injury he sustained at the Cheltenham Festival.
Russell partnered Lord Windermere to win the RSA Chase on the Wednesday of Cheltenham, but suffered a heavy final-flight fall from Un Beau Matin in the Coral Cup later in the afternoon.
Although he returned to action the following day, Russell had to be taken to Cheltenham General Hospital for treatment after two rides, when it was revealed he had sustained a punctured lung.
After receiving medical clearance in Ireland and opting to postpone further treatment until the end of the season, he was back in action on the Thursday after Cheltenham, partnering Rebel Fitz to finish second at Cork, and has four booked rides on the first day of the Fairyhouse Easter Festival on Sunday.
However, Russell revealed to RTE Radio 1 that he would not be allowed to ride in Britain, where the three-day National fixture starts on Thursday.
His agent Andrew 'Frosty' Kelly said: "He went to London on Thursday to see the BHA's specialists and they just wouldn't pass him.
"He's ridden since the injury, is riding tomorrow and feels 100% - he was really looking forward to going over to Aintree. It seems a strange decision, but Dr (Michael) Turner just wouldn't pass him.
"His ride in the National was still to be confirmed but he'd have been on the likes of Solwhit (Aintree Hurdle) and Quito De La Roque (Betfred Bowl), so he's missing some nice rides."