Prime Minister Boris Johnson has confirmed that initial plans for spectators to return to sporting events from October 1 will not now go ahead.
The decision comes as a big blow to racing, with Newmarket all set to welcome crowds of up to 1,000 at each of the three days of its Cambridgeshire meting - which begins on Thursday.
Prime Minister Johnson also stated that the new restrictions coming into place may last for "perhaps six months".
The latest course of action has been brought about by a rising coronavirus infection rate.
Speaking on Tuesday lunchtime in the House of Commons, Prime Minister Johnson said: "We have to acknowledge that the spread of the virus is now affecting our ability to reopen business conferences, exhibitions and large sporting events, so we will not be able to do this from October 1 and I recognise the implications for our sports clubs which are the life and soul of our communities."
He added: "We will spare no effort in developing vaccines, treatments, new forms of mass-testing but unless we palpably make progress we should assume that the restrictions that I have announced will remain in place for perhaps six months.
"For the time being, this virus is a fact of our lives and I must tell the
House and the country that our fight against it will continue."
The announcement comes barely 24 hours after Warwick staged a successful pilot event, with around 450 spectators on track.