Carlisle United's league opener with Cambridge will now be played behind closed doors after a pilot event for the return of fans was cancelled.

It was originally intended that home fans could watch Saturday's game at the Abbey Stadium as a test event for the safe return to supporters to league grounds.

Cambridge, though, said they have shelved the plan after last night's new Government guidance over Covid-19, and after consultation with health authorities.

Cambridge said they had initially planned for a crowd of 2,000, but that capacity had been halved by the Prime minister's announcement.

"In discussion with relevant safety authorities, the club has had to take the difficult and disappointing decision to play behind closed doors," Cambridge said in a statement.

"This is no one’s fault - and everyone recognises that the national situation has changed - but it was felt that we would have been left with too many invalid tickets in circulation for a game where safety has to be the number one priority.

"Even with reticketing and regular direct communication to all fans over the next 24 hours, the short timeline means that the club cannot entirely mitigate the risk to fans and stewards of people arriving in good faith for the game with tickets that are invalid and being unable to attend given the reduced capacity.

"Therefore, whilst it is a difficult decision to cancel the pilot, it is the right one in circumstances where we must all prioritise public health and safety."

They added: "We have not ruled out the possibility of holding another test event in the coming weeks with a 1,000 capacity."

Cambridge had last night said they were seeking more guidance following the Government's tightening of coronavirus restrictions.

The club had 862 fans at their ground for Tuesday's EFL Trophy game against Fulham's Under-21s, the first crowd at an "elite" football game in the UK since March.

The Abbey Stadium club had been making arrangements for season-ticket holders to attend the Blues fixture, providing e-tickets to seated season-ticket holders and giving terrace season-ticket holders the opportunity to use their season cards.

General sale tickets were due to be available from today. No away supporters would have been allowed to attend.

The Department for Digital, Culture, Media and Sport issued guidelines yesterday saying that sport pilot events would now be limited to 1,000 spectators in light of the recent increase in coronavirus cases.

The new measures have thrown into doubt plans to have fans back into all stadiums by October. The Government said such aims are under review.

New measures aimed at reducing the virus's spread mean people in England must not meet socially in groups of more than six people, indoors or outdoors.

Speaking earlier this week, a firm commissioned by the EFL and the Sports Ground Safety Authority (SGSA) to assess the the application of social distancing guidance at football grounds said it had been working on plans to help clubs welcome fans back to their grounds.

Movement Strategies say they had provided a “how to” guide for EFL clubs developing social distancing plans, including the process for calculating safe capacity.

They said this included a number of considerations, also including concourse capacities, entry and exit capacity calculations, areas immediately outside venues, and toilet, food, hospitality and retail areas.

The firm have also been attending pilot schemes at other events such as the World Snooker Championship at Sheffield’s Crucible Theatre.

Dr Aoife Hunt, associate director at Movement Strategies, said: “The SGSA’s social distancing guidance provides venue operators with a much-needed planning toolkit to enable the re-admittance of spectators to live sport.

"The case studies at Charlton Athletic and Cambridge United were an important step to ensure this guidance can successfully be applied to real-life grounds.

"There are so many factors that venues have to take into consideration when planning for the return of fans, and it’s our job to help make the process as straightforward as possibly by providing them with all the information and guidance they need to determine a new safe capacity and get the right social distancing measures in place.

"We are proud to now be working alongside clubs from the Premier League, the EFL and the National League, as well as other venue operators across the UK, as they prepare to safely re-open their doors to fans once they are permitted to do so.”

Martyn Henderson, chief executive of SGSA, added: “This is a hugely valuable piece of work. We’re in unprecedented times and this study offers valuable insights that will help grounds anticipate and address the challenges involved."

Speaking after today's announcement of the postponed pilot event, Cambridge chief executive Ian Mather said: "We understand there will be disappointment from our supporters, but we hope they will recognise the reasoning as safety of all stakeholders has to be our key concern.

"We have looked long and hard at different solutions and held a number of discussions with the public health and safety authorities, but it is not possible to mitigate the obvious risks given the change overnight to capacity.

"Cambridge United remain very proud of the collective achievement on Tuesday night and must reiterate the football club’s immense gratitude to the supporters whose exceptional co-operation contributed majorly to the evening’s success.

"We are hopeful that the knowledge and learnings gained will allow the return of supporters to stadiums across the country as soon as possible, and Cambridge United stands ready to participate in future pilots to accelerate that process at the appropriate time."