Like most pioneers, the first Lewis motorcycles were unsprung.
By the time serious manufacture of motorcycles began around 1903 the standard Lewis front fork was a braced Chater Lea item, with the bracing struts extending from the top of the steering column (where they fitted into recesses in a bolt-on crown) to a specially designed axle lug. Another brazed lug joined the bracing struts to the fork legs just below the main crown. This robust fork design was used on all Lewis machines, little changed, through to 1910.
At the Autumn Show in March 1907 the Lewis motorcycles on display featured front suspension for the first time, by virtue of a leaf-spring attachment bolted to the existing rigid fork.
So what was the origin of the Lewis spring fork? The design can be traced back to two Frenchmen, Louis Masi and Célestin Vigneaux, who were granted a patent for it in January 1904. Clearly the inventors, who described themselves as "Agents for Manufacturers", had more than the French market in mind, for they also patented the design in England with GB patent No. 10,331 issued on July 4, 1904. The patent describes exactly the fork used by Lewis, in which two vertical members carrying the front axle slide under the control of a leaf spring. In the Lewis implementation, the original Chater Lea rigid fork is retained unchanged.
The Masi and Vigneaux fork was marketed quite successfully in Europe, where it was used by large manufacturers such as Griffon and Alcyon from 1904 and Minerva from 1905. In some if not all of these applications, the fork was referred to as the "Simplex" fork. A surviving Minerva has "Simplex" stamped on one of the leaf springs.
It might be tempting to think that a version of the M&V fork was sold by Chater Lea, but this doesn't seem to be the case. The 1907 Chater Lea catalogue shows a spring fork but it is not the M&V design, instead using short pivoted arms at the fork ends, with the axle carried forward of the pivot and springs in tension, at the rear of each fork leg, attached to the rear. A number of British manufacturers used this early Chater Lea sprung fork, including Chater Lea themselves, but few if any adopted the M&V fork. In Australia it was rarely seen other than on Lewis machines. Had the M&V fork been marketed by Chater Lea, it would surely have had wider use in the British Empire.
The most likely origin of the Lewis leaf-spring fork is that it was a locally built copy of the M&V design. The square boss that anchors the leaves under the steering head is delightfully agricultural (featuring a coarse Whitworth thread), the leaves themselves lack the delicate tapering of the "true" M&V fork, and the vertical tubes have simple crimped ends where they attach to the front of the spring. European versions have a forging in this area.
The leaf spring design did good service at Lewis, lasting well into 1910. Machines on the Lewis stand at the Spring Show in September 1910 has many new features, including the new Precision engine and "the well-known Chaterlea spring forks". Actually it would be surprising if the forks themselves were "well-known" at the time. Although William Chater Lea obtained GB patent No. 27,797 to protect his design in September 1909, it's doubtful that this fork was widely used in Australia before being adopted by Lewis. Nevertheless the Chater Lea brand was a strong one and Lewis leaned on it often in promoting their bicycles and motorcycles. This fork style - with the leading link controlled by vertical coil springs parallel with the steering head - was used by Lewis well into the war years, and perhaps occasionally beyond. The first mention of Lewis motorcycles with the Druid fork - essentially the standard fork for Australian manufacturers since about 1910 - was in 1916 when in an article about a 3 h.p. lightweight model it was noted that the Druid fork was in use "throughout". Throughout the model range perhaps? Most likely there were a mix of forks used in the late war years, with the Chater Lea fork disappearing around 1918.