All sporting events in Wales will be held behind closed doors from St Stephen's Day due to the surge in coronavirus cases, the Welsh government has announced.
Sports events in Scotland will be restricted to a maximum of 500 spectators for "up to three weeks".
Welsh Economy Minister Vaughan Gething announced the new measures for indoor and outdoor sporting events in a bid to slow the spread of the Omicron variant.
Gething said: "Sporting events over the Christmas period are one of the big highlights of the year. Unfortunately, the new Omicron variant is a significant development in the pandemic and could cause a large number of infections.
"We need to do everything we can to protect people's health and control the spread of this awful virus.
Chepstow Racecourse chief executive Phil Bell anticipated the move last week, when he told BBC Wales: "We've seen this coming in recent days.
"It would be damaging - we've currently sold 6,000 tickets - an average price £35 - so people can do the maths. Around 800 people have booked hospitality packages at around £80 to £120 - there are significant amounts of revenue at stake here."
In Scotland First Minister Nicola Sturgeon delivered the update following a Cabinet meeting to discuss ways of slowing the spread of the Omicron variant of Covid-19.
New rules will kick in on St Stephen's Day and impact the festive football fixtures, which include top-flight derbies in Glasgow, Edinburgh and Dundee in the first few days of 2022.
They will also affect the double-header between Glasgow Warriors and Edinburgh in the United Rugby Championship.
Sturgeon said: "From December 26 inclusive, for a period of up to three weeks, we intend to place limits on the size of live public events."
Indoor standing events will be limited to 100 spectators, indoor seated events to 200, and outdoor events to 500 people with physical distancing of one metre in place.