The precision marching of the People’s Liberation Army at yesterday’s parade was immaculate, according to the most senior drill instructor in the British Army.

Garrison Sergeant-Major William Mott, who has more than 25 years under his belt training the British Guards Division for ceremonial duties at Buckingham Palace, was thoroughly impressed by the 200,000-strong parade through Tiananmen Square. “With a width of 25 men it is very difficult to maintain the kind of dressing they have achieved,” he said. “After about six or seven people width, dressing becomes very hard.”

Dressing is the technical term for the precision with which soldiers can march in line abreast. It is an exact science. Warrant Officer Mott, like all Guards Division drill instructors, uses a pace stick, shaped like a giant pair of adjustable compasses, to train guardsmen to march 33 abreast at precise 30in paces and 116 steps per minute.

The Chinese appeared to have maximised their chance of achieving near-perfect precision by sizing soldiers to ensure that they were of identical height.

“If you have identical sizing then you get the same leg length and pace length,” said Warrant Officer Mott, spotting the uniformity of height across the ranks. Such practice used to be common in some British regiments. The Prince of Wales’s Company of the Welsh Guards — Warrant Officer Mott’s own — were all once selected to be at least 6ft. These days the Guards regiments put the tallest soldiers at the outside of the ranks and taper gradually towards the shortest in the middle. The eye tends to even out the difference.

The flat paving in Tiananmen Square helped the precision of the Chinese marching, and the female soldiers photographed were given a less demanding task by being allowed to carry a weapon against their chest rather than swinging their arms.

“The men in this photograph, the arms to the rear aren’t perfectly uniform, but you will naturally get some difference in height range with the arms.

“It is not possible to get it better than they have. You are limited in the precision you can get by the human character.”

Warrant Officer Mott also noted that in a simple march-past it was possible to attain far higher standards of precision than if complex manoeuvres were attempted. “They won’t be doing any sequences here. They would be just going once through the square,” he concluded.

“If they had done any manoeuvres, then it would be impossible to get the dressing they have.

“It comes down to self-discipline and having a long time to practise if you are to get that standard.” In this instance, he estimated, it took the Chinese soldiers at least two months of daily toil.