Which kind of headbutt was Bairstow's?

'Jonny has been himself' - Woakes (2:29)

Chris Woakes confirmed a curfew had been put in place following the Jonny Bairstow headbutt incident (2:29)

Trevor Bayliss, the England coach, has insisted what Jonny Bairstow did to Cameron Bancroft during a night out in Perth cannot be classified as a headbutt, even though he admits there was contact between the two players' heads. Bancroft, meanwhile, in a bizarre press conference in Brisbane following Australia's victory in the first Test of the ongoing Ashes series, said it was a butt, albeit a playful one.

So why the confusion? In the interests of harmony, as relations between Australia and England become increasingly fraught, we have produced a useful guide.

Well, it's not always easy to judge what is a butt and what's not. Just ask football referees, who have to make decisions regularly to issue a red card or just view a collision as one of those things. We've scoured a list of suspected headbutts from various sports and deciphered that there are four main types of butts.

Some are easy to spot, while others leave space for the kind of ambiguity surrounding Bairstow's. So here we go. Which do you think it was?

The Full-Blown Moving Butt

The most famous example of this type was Zinedine Zidane's headbutt to Italy defender Marco Materazzi in the 2006 football World Cup final. Zidane, then considered the best footballer in the world, drove his head into Materazzi's chest and was sent off by the referee. As you can see from the illustration of the event, Zidane prepared for the butt when he was a few feet away from Materazzi, bending his left knee and preparing to spring forward. He then got his whole body into the strike, arching his back and bending forward as he delivered the blow. A moving headbutt is pretty easy to spot, and there's no questioning that it is in fact a butt.

The Standing Butt
This occurs when two sportsmen are standing in close proximity, often amid a melee of other players, and one makes a slight, surreptitious neck movement towards the other to make contact with his head. There's no movement of the legs or back in this kind of butt, which makes it harder to detect. Also, it's sometimes tough to tell whether a player has meant to butt the other or just square up, brow to brow, and say hello. In the incident depicted above, for example, Marouane Fellaini, the Manchester United midfielder, appeared to just slowly lower his head onto that of Sergio Aguero, the Manchester City forward. Whether or not a standing butt is considered a butt at all really depends on the speed and intensity of the neck movement. But it can be confusing. Fellaini was sent off for his slow nod, but when Luis Figo, the Portuguese footballer, made a sharp snapping motion with his neck to deliver a standing headbutt to Netherlands midfielder Mark van Bommel in a 2006 World Cup game, he was given just a yellow card.

The Head Push
This is the kind of thing you'll often see when two mates are simply joshing around, as Bairstow says he was doing with Bancroft. One person places his head on the other's and then pushes forward, making it more of a head push than a headbutt. This rarely causes any sort of injury or harm, but can be used as a means of intimidation. Joe Hart, the England goalkeeper, received a yellow card for a head push on footballer George Boyd in a Premier League match. As you can see from the depiction above, Hart starts with his head already touching Boyd's and then stretches his neck forward.

The Head Uppercut
Some headbutt aficionados on social media have pointed out that Bairstow is shorter than Bancroft and would have had trouble executing a butt. Well, perhaps he employed the uppercut technique, as American boxer Victor Ortiz did in his bout against Floyd Mayweather Junior. As seen in the depiction above, this butt is delivered by a shorter man crouching down and then springing upwards to smash his head into a taller man's jaw or forehead. Argentinian footballer Ariel Ortega used a variation of this butt against Netherlands goalkeeper Edwin van der Saar, who is almost a foot taller than him, in the 1998 World Cup quarter-final. Ortega was sat on the ground, and when van der Saar bent down to harangue him about diving, Ortega sprang up and smashed his head into the big man's jaw.

So which of these techniques did Bairstow use against Bancroft? Was it a full-blooded head uppercut or just a little head push? Perhaps it was none of them and we need a new category - the Bar Room Butt perhaps.

Hopefully, both men will be focused solely on their batting techniques by the next Test, in Adelaide.