On 3 October 1925 Arsenal lost 0-7 to Newcastle, and Arsenal’s manager, Herbert Chapman immediately began discussions to transform Arsenal’s tactics.  Buchan in his autobiography claimed that he was the key adviser to Chapman in this, but it seems from other sources that several others were involved in the discussion – which was about far more than pulling the centre half deeper down the pitch to play between the two full backs, as Charlie Buchan suggested in his book.

Certainly, it seems that there is good reason to believe that Joe Shaw, the ex-Arsenal player and now Reserve team coach, and Tom Whittaker, also an ex-player and now recovering from the career-ending injury sustained playing for an FA XI in Australia, were both involved in consultations – although perhaps not in the final decision making.

The “WM” system is often considered to be, consisted of a simple move to pull the centre half of the old approach (who carried the number 5 and played in the middle of the midfield) back into the middle of the defence.

In fact there are two things wrong with this view.  First, there is clear evidence that some teams were already pulling the centre half deeper into the back line before 1925.  And second, the front five had not been playing as a straight line of attackers for many years.  Instead the general approach was a 2-3-2-3 line up, morphing into 3 2 2 3 when the centre half moved into the back line.

However, countering this view, Buchan says (page 95 of his autobiography) that “New methods were required and Arsenal were the first to exploit them”.

It is probably this phrase that has led to commentators believing that Buchan was talking about the WM tactical formation – but it turns out he wasn’t, for he subsequently says,

“It has many times been said that the change in law brought into operation the ‘stopper’ centre half, but there were many such ‘stoppers’ long before that eventful day.”  He then proceeds to mention four of the most famous centre halves who played in the final line of defence between the two fullbacks before the 1925 law change.

On page 97 Buchan moves on to the post-match meeting after the 7-0 defeat on 3 October 1925, held in the Newcastle hotel.  Buchan reports that he had been pressing for a change to the way Arsenal lined up since he was transferred to the club in the summer of 1925 and says that finally, after this game, Chapman asked him to explain his views more fully.

Buchan’s first point was not to have a centre-half playing between the full-backs, and marking the opposition’s number 9, but rather to have him guarding the edge of the penalty area.   Buchan was, in fact, inventing zonal marking for this player, leaving the others free to cover the flow of the play.

Now that notion of the centre half patrolling zonally does give us a “W” defence.  Moving across the W from left to right we have the left top of the W as the left half, the left bottom as the left back, the midpoint neither as high as the left half nor as low as the left back – that is the new “centre half position”, and then the right side of the the W – the right back and the right half.

So here is the invention of WM, and it was (it seems) the invention of Buchan not Chapman.  But we must be clear, WM does not mean pulling the centre half back to play between the two full backs, because other clubs were doing that already.  Instead it means playing the centre half further away from the goal line than the full backs.

But that was not all.  What Buchan also wanted was that the centre half should be a “dominating personality around his own goal.  And he should not be content just to get the ball away anywhere, but to send it, with head or feet, to the roving inside-forward”.

So, an end to the big man hoofing it up the field and instead centre halfs who knew where to put the ball.

Thus now comes the next part of the equation: the “roving inside forward” – part of the “M” in the equation.  Buchan nominated Andy Neil – a man who could receive the ball with either foot and pass it on quickly to get the counterattack going, resulting in a goal from three or four touches out of defence.

This is much more than WM – this is zonal marking with a centre half who would always find one particular player who had the skill to move the ball on at once for the counterattack.  It was a system ultimately perfected with Herbie Roberts at centre half, passing to Alex James who moved the ball instantly on to Joe Hulme or Cliff Bastin.

As Buchan says, “the novelty of Arsenal’s new methods took the other League clubs by surprise,” and by Christmas Arsenal were top of the league.  Indeed but for illness and injury Arsenal would probably have won the league in Chapman’s first season.  As it was they had to settle for second.

• Arsenal Day by Day: the stories
• Arsenal in October: Over 600 Arsenal events day by day 
• 100 Years: 100 Years in the First Division