Video Assistant Referee (VAR) technology is once again in the spotlight after a farcical night at Wembley as Tottenham played Rochdale in a FA Cup replay.
Referee Paul Tierney disallowed a first-half goal scored by Tottenham's Erik Lamela with a mystifying VAR call and then ruled out a Son Heung-min penalty due to 'illegal feinting'.
It wasn't the first time the VAR has left fans, players, coaches and television viewers utterly bemused, and Tottenham manager Mauricio Pochettino has said it will 'kill emotion in football.'
We take a closer look at what all the fuss is about and what can be done to improve a currently flawed system.
Video Assistant Referee technology caused confusion in Tottenham's match with Rochdale
Referee Paul Tierney makes the 'square in the air' signal for a VAR decision at Wembley
Before we look at the drawbacks, why was VAR brought in and how does it work?
For the uninitiated, VAR stands for Video Assistant Referee and is a new system designed to reduce the number of officiating errors in football.
It is a team of three people working together to review certain decisions made by the on-pitch refree by watching video replays of an incident.
The team comprises of a video assistant referee - who is always a current or former referee - his assistant and a replay operator, sat in a video operation room usually away from the stadium.
They are in contact with the referee on the pitch via a microphone and an earpiece.
Four types of decision can be reviewed using VAR:Goals and whether there was a violation during the build-up Penalty decisions Red card decisions (but not second yellow cards) Cases of mistaken identity when issuing a card
A TV monitor for VAR decisions pitchside at Wembley for last Sunday's Carabao Cup final
For a decision made on the pitch to be overturned, it needs to be a 'clear error', according to the rules laid out by the International Football Association Board (IFAB).
The VAR process for reviewing a decision can be initiated either by the on-field referee requesting a review having made a decision, or a recommendation by the VAR team watching on television.
After a VAR review, the referee has three options: immediately overturn their decision based on VAR advice, review the incident themselves on a TV monitor on the touchline, or stick with their initial decision.
VAR isn't yet written into the laws of the game, with a vote on that due this Saturday, but it is currently being trialled in a number of competitions around the world.
Italian ref Gianluca Manganiello consults the VAR monitor during the Sassuolo-Lazio game
I keep hearing 'Stockley Park' mentioned in commentary - what are they referring to?
The VAR hub for matches played in England is located at the Premier League Match Centre in Stockley Park, which is located in west London, a short drive from Heathrow Airport.
This is where the VAR teams will gather to watch matches from many different angles on a bank of television monitors and communicate with the referees in the thick of the action via headsets.
The VAR officials will be named as part of the officiating team from now on, so fans at least know who is making these calls remotely.
Where did it make its debut in English football?
The first match in England to use VAR was the international friendly between England and Germany played at Wembley on November 10 last year.
The first club fixture to deploy VAR was the FA Cup third round tie between Brighton and Hove Albion and Crystal Palace at the Amex Stadium on January 8 this year.
It has since been used in various other FA Cup fixtures and the EFL Cup semi-final between Arsenal and Chelsea, and the final between Arsenal and Manchester City last Sunday.
Referee Jonathan Moss signals for a VAR review - the system is being trialled in England
What have been the big controversies before Wembley last night?
There have been quite a few. In the FA Cup third round replay between Chelsea and Norwich City at Stamford Bridge, home fans were left fuming at referee Graham Scott when he booked Willian for a 'dive' in extra time.
Millions of viewers watching replays on TV were convinced that the Brazilian had been fouled by Norwich defender Timm Klose but VAR official Mike Jones, supposedly watching the same replays, told Scott no review was necessary.
It didn't help that Scott subsequently dismissed Chelsea players Pedro and Alvaro Morata, both having picked up their first bookings for diving, though Chelsea ultimately advanced on penalties.
In the Liverpool vs West Brom fourth round tie, regular VAR referrals by referee Craig Pawson disrupted the contest, much to the frustration of fans both at Anfield and watching in television.
Pawson disallowed a Craig Dawson goal for offside and then took four minutes to decide that Jake Livermore's challenge on Mohamed Salah should be a penalty.
Craig Pawson on one of his many VAR checks during the Liverpool vs West Brom FA Cup tie
And in the Huddersfield vs Manchester United fifth round tie, Juan Mata had a goal disallowed for a marginal offside but TV viewers were shown a confusing replay with wiggly lines across the pitch.
But there have been plus points to VAR. Leicester's Kelechi Iheanacho will always have the distinction of scoring the first VAR-awarded goal in English football.
The Nigerian striker was initially flagged offside when he scored, but a check of the replays showed he was actually onside and the decision was overturned.
The wobbly VAR lines that adjudged Juan Mata offside in the Huddersfield vs Man United game
And what went wrong at this Tottenham v Rochdale match?
There were three incidents at Wembley that caused confusion, in particular for the fans inside the stadium.
Spurs thought they had a sixth-minute lead when Erik Lamela scored, but VAR decided that Fernando Llorente had fouled Harrison McGahey in the build-up and the goal was chalked off.
It took about 90 seconds for the alleged infringement by Llorente, harsh in any case, to be checked by the VAR panel and for referee Paul Tierney to disallow it.
Then, after 25 minutes, Rochdale's Matt Done hauled down Kieran Trippier and the linesman flagged for a Spurs free-kick on the edge of the area.
However, the VAR officials decided the offence actually took place inside the area and, after several minutes of deliberation, Tierney changed the decision and pointed for a penalty.
Paul Tierney, finger to earpiece, waits for a decision from the VAR officials on Wednesday
Son Heung-min then stepped up to take the penalty and scored, but the South Korean stuttered in his run-up, a distraction tactic that has been outlawed.
Tierney, with the help of VAR and another delay, disallowed the goal for so-called 'illegal feinting' and the Spurs player was booked.
It led to five minutes of injury time being added on at the end of the first-half for all the VAR delays and yet more condemnation from managers and pundits alike.
You also have the annoying situation where fans - and players including Son - make the VAR signal whenever something contentious happens.
Tottenham's Son Heung-min makes the 'square in the air' signal to referee Paul Tierney
Pochettino said: 'Football is about emotion. It is a contest of emotion and if we are going to kill emotion in football, the fans, the people who love football, are not happy about what they saw.'
BT Sport pundit Robbie Savage labelled it 'one of the most bizarre, entertaining, shambolic first-halves I have ever seen in my life.'
Alongside him, Jermaine Jenas described it as 'an absolute shambles'
Spurs legend Ossie Ardiles added on Twitter: