In the William Foster and Co. Ltd engine record book for late 1917 there are several entries for engines intended for a new tank, designated the Mk VI. This seems a little odd at first glance as the Mk VI was a heavy tank proposed in June 1917. The Mk VI had only gone as far as the wooden mock-up stage before being cancelled. The tank was such a radical departure from the heavy rhomboids of the time that the project came to nothing, so why were Fosters mentioning the Mk VI in their order books?

The mystery is solved when one sees the word ‘Hornet’ on the next page. The tank was actually nothing whatsoever to do with the old Mk VI and was instead the latest in a line of machines known as Medium tanks. Once the heavy tanks had breached the trenches, the Mediums would come to the fore and chase the German army back to Berlin at terrific speed, well that was the plan anyway!

The Medium tanks of the Great War were the Medium A Whippet, the Medium B and the Medium C Hornet. The Medium A saw action in the last year of the war and they and their crews did sterling service in many battles. The next tank was the

Medium B, often cruelly described as the ‘ill-fated Medium B’. The heavy tanks were designed at William Fosters factory in Lincoln by a team headed up by two men, William Tritton,

Managing Director of the company and Major Walter Wilson RNAS, who had been sent by the Army to oversee proceedings and give things a more military air. The two men worked well together, but the Medium B was to be the first Great War tank designed by Walter Wilson alone.

He was a brilliant engineer and an inspired designer, but although the Medium B was full of good ideas, the entire package was a bit of a disappointment. Wilson was all too aware of the problems of moving tanks by rail and he decided to make the new machine as short as possible so that it could be driven onto just about any standard flat railway truck. Unfortunately, the length of the tank left interior space in short supply and both the engine and fighting compartments were very cramped indeed. There was no access to the specially shortened 4-cylinder Ricardo engine via the crew compartment, so a problem with the engine would mean the crew having to exit the tank under fire to get under the bonnet. There were several other problems with the tank and of the 700 ordered, a total of just 80 were produced by The Metropolitan Carriage, Wagon and Finance Co. of Birmingham, Coventry Ordnance of Glasgow and the North British Locomotive Co. of Glasgow before the order was cancelled. It may not have seen action in France, but several Medium C tanks, Mk V machines and Medium A Whippets were given to the White Russians.

In a remarkably logical piece of military thinking, the next of the Medium machines after the B would be known as the Medium C. It would be designed by William Tritton without input from Wilson and was built by William Foster and Co. Ltd of Lincoln. It shouldn’t be assumed that Tritton and Wilson fell out over their separate designs; in fact there was apparently some good-humoured rivalry between the two men, who remained firm friends. The Medium C was originally known at the factory as the Hornet, but this never seems to have been an official military title. It is often described as the best tank of the era as Tritton and the design team from Fosters combined all the best ideas and experience of three years of tank building when he created the new machine and it was packed full of new thinking and clever technology.

Instead of the old 105hp Daimler Sleeve Valve engine used on the early British Tanks, the Medium C was powered by the full size 6-cylinder 150hp Ricardo that had already seen service in the Mk V and some late model Mk IV machines. The Daimler had been a compromise as it had not been intended for use in tanks, but the new engine, designed by the brilliant Harry Ricardo was purpose built for tanks and despite increased interior working temperatures the new power plant was perfect for the new generation of machines.

It may not sound particularly special, but the Medium C could boast a completely separate engine compartment with a partition between it and the crew compartment. This meant that for the first time, the crew were much less likely to be asphyxiated by fumes from their own exhaust. It is an often-quoted fact that Tank Corps losses in the Great War were around 40 percent and more men were killed by carbon monoxide poisoning than they were by enemy fire. The engine now being separate to the crew also made for a much quieter environment and each position was linked by a voice tube, negating the age old practice of relaying coded orders by banging a large spanner on the tanks engine casing.

Like most other tanks of the late war period, the Medium C could be driven by just one man, and it had five ball mountings that each took a .303 Hotchkiss machine gun. The complete armament of a Medium C Hornet was made up entirely of machine guns, which officially designated the tanks as ‘Females’. There had been a plan to make a ‘Male’ version with a six-pound gun at the front of the cab, but the variant never went beyond the drawing board. The Medium C had room for five machine guns, but only four were fitted. There was also a mounting in the roof of the cab so that if the tank was attacked by enemy aircraft one of the four guns could be moved into this position and the top hatch could be flung open to return fire. This fitment had also been seen on Wilsons Medium B, so perhaps there was a bit of collaboration between the two supposedly separate projects after all?

Unfortunately, the anti-aircraft hatch would leave the gunner completely exposed to both aerial and ground fire, so it would have been unlikely that the hatch would ever have been used for its intended purpose. Behind the hatch was a rotating hexagonal cupola, just big enough to get your head in, which would give the Commander a 360-degree view all around the tank. The cupola was a good idea, but pushed the finished tank over the standard railway loading height and would have needed to be removed prior to train travel.

The Commander had his own fold down map table, a compass of the type used in aircraft and there even was a distance indicator, which was driven off the tanks final drive. There was a charge of gun cotton placed next to the gearbox so that the tank could be destroyed instead of falling into enemy hands and perhaps most impressive of all, the new tank had its own doorbell so that troops outside could attract the attention of the crew inside. The Medium C also had the ability to create its own smoke screen thanks to a reservoir of Sulphonic Acid which could be squirted into the machines hot exhaust, this system was another device that had been fitted to some Mk V* machines and also Wilsons Medium B.

The War Office were suitably impressed with Trittons Medium C Hornet and placed an order for 200 machines. In October 1918, further orders were placed with various factories for both female and male machines, but these were all immediately cancelled leaving Fosters the only factory to produce finished Medium C tanks. It is a shame that the tank could not have been tested in battle, but by the time it was ready, things were coming to an end, we had the Germans on the run and there was no point in shipping new tanks out to the Western Front when the war would have been over before they arrived. At a Royal Commission hearing in 1919 William Tritton was asked why the Medium C had taken so long to come into service? He replied that ‘many months had been lost on tank production due to the failure of the Mechanical Warfare Supply Department to deliver parts. The Ministry had promised engines and gearboxes, but the delivery fell further and further behind until the delay wa: well over a year’. Several factories, such as Ruston and Hornsby in both Lincoln and Grantham, built the Ricardo engine under licence, but the shortages became worse and worse until the Medium C gained its unofficial title of ‘the best the tank never to see action’. By February 191 William Foster and Co had delivered just 36 out of the 200 machines ordered and soon afterwards, the contract for the remaining 164 was cancelled. Some sources say that a further 14 to 18 Medium C tanks wer created using parts collected together from the other factories whose contracts had been cancelled, but details are sketchy and it is unclear if this is actually true and if so, which company actually assembled them.

The Medium C officially went oul of service in 1923 although several remained with the Army until the mic 1920s and the last remaining example was apparently sliced up during the scrap metal drive of early World War 2. The Medium C Hornet may never have seen action, but is a significant milestone in the story of British Tank design and can quite rightly take its position as the missing link between the early heavy rhomboids and the more conventional, modem designs that followed it.

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