It’s the moment nobody’s been waiting for but most agree had to arrive at some point: the Video Assistant Referee is finally coming to the Premier League. This season, thanks to a colleague in an industrial estate in west London, referees will be able to correct bad decisions during a match and create a better, fairer style of football. Well, that’s the plan anyway.

As anyone who watched the Women’s World Cup this summer will know, VAR is no silver bullet for bad refereeing decisions. It can in fact make things worse, whether by causing delays or overturning referee’s decisions for the most marginal of reasons. In principle, though, it’s simple enough: the Video Assistant Referee is an extra official who watches a match from as many angles as there are cameras and informs the referee on the pitch if he or she has made a “clear and obvious” error in one of four crucial decisions (awarding a goal, a penalty, a red card, or in a case of mistaken identity). The big question is how you make that work in practice.

New world order? Welcome to Premier League's new era of excellence Read more

Just before the start of this season every Premier League manager was invited to VAR HQ in Stockley Park, not too far from Heathrow. There they were given a walk-through of how the technology is to be used this year, a plan that follows the culmination of two years of training and a delayed launch which allowed time to watch others get it wrong first.

The guiding principle of VAR in the Premier League is that it should interfere as little as possible. For a competition that prides itself on being fast, furious and dramatic, there are serious concerns about disrupting a match to the extent that games might be extended for up to 10 minutes (as they were during the Women’s World Cup).

This principle, it has to be said, is what VAR was always supposed to be about. “Maximum benefit, minimum interference” is the phrase used by the International Football Association Board, the body that devised the basic protocols of VAR. It hasn’t always worked like that though and the Premier League hopes a clear message to VARs and some tweaks in how the rules are applied could make a positive difference.

This starts with VARs being told they are not there to re-referee a match. Sitting at their hub in Stockley Park they will watch the match as live alongside an assistant VAR and a Recording Operator (RO). When incidents occur within the four categories listed above, they will inform the referee on the pitch that a check is occurring. They will then review footage from as many angles as is necessary until they are satisfied that no error of the “clear and obvious” variety has occurred (while the VAR does that the assistant will take over watching live, just in case there’s another incident in the meantime). When the check is complete, the VAR will press a big red button on their desk and inform the referee of any new information that might effect their decision. After that, it is up to the ref to make the final call .

Some errors are objectively observable and therefore more easily correctible. These are situations such as whether a player is offside before a goal is scored, or if a foul adjudged to be a penalty was actually made in the area or just outside it. Some of these calls can be decided simply by checking footage. In the case of offside, the RO will be able to generate a 3D line pinned to the attacker’s most advanced bodypart (arms don’t count) to give their VAR a definitive reading. That information is then fed, via the big red button, back to the ref.

It’s with decisions that will always be subjective that things start to get more complicated. Take tackling, for example. A sliding challenge with studs up on one foot could be interpreted by the referee as being “reckless” under Rule 12 and therefore deserving of a yellow card. He might alternatively decide, however, that the tackle “endangered the safety of an opponent” and was therefore deserving of a red.

In these circumstances the VAR will have their own opinion and will have had access to many more camera angles with which to inform it. But again they will be instructed to defer to the referee unless the high bar for “clear and obvious error” is met. If the referee has seen the foul and decided it’s not that bad, no amount of slo-mo rewinds from a particularly gruesome angle should persuade a VAR to intervene.

Facebook Twitter Pinterest A VAR screen pitchside at the Liberty Stadium. Photograph: Athena Pictures/Getty Images

Crucial to any such decision-making will be communication. A referee is expected to give his VAR a running commentary on the reasons behind the decisions he makes. So if the referee calls “reckless” rather than “endangering” he will explain his reasons for doing so. The VAR might then disagree with the interpretation but, unless they had seen something the referee had not, they would be unable to state clearly that an error had been made.

That is the principle, though nobody in the Premier League or the refereeing body, Professional Game Match Officials Limited, is under any illusions that there won’t be controversy. A new raft of potentially headline generating rules – the “unnaturally bigger” handball law amongst them – will lead to uncertainty.

Also look out for lots of heated debate as to quite what constitutes the “attacking phase of play”. Any foul or infraction missed by the referee in the buildup to a goal could cause it to be overturned by VAR. The question, however, is when you start the clock. One of the components the Premier League have settled on for determining this point is the “ability of the defence to reset”. What constitutes a reset? And if you try but fail is that expressing your “ability”? Expect to hear many opinions on such matters soon enough.

The Fiver: sign up and get our daily football email.

There will be no shortage of talking points, including amongst pundits who will wilfully misinterpret the odd decision now and again just for the sake of it (little detail: TV directors will be able to listen to the dialogue between referee and VAR, though viewers won’t). Not only is the Premier League expecting this, they’re sort of content with it; controversy is what keeps the show on the road between matches.

Finally, there’s the group who have so often been an afterthought during the development of VAR, the fans in the stadium. The Premier League have decided that checks will be announced to fans via graphics on the big screen (in all grounds apart from Anfield and Old Trafford, that is, because weirdly they don’t have big screens). If a decision is overturned, the offending piece of footage will be then be shown too. That, you can imagine, could provide the odd moment of unexpected theatre.

This is how it’s all going to look, at the beginning, as top-flight English football embraces video technology at last. The emphasis is on enabling referees, on keeping disruption to a minimum and, of course, making more correct decisions. Time will tell how well that works, but one thing is for certain: there’s no turning back now.