It could survive the machine gun and small-arms fire in "no man's land", travel over difficult terrain, crush barbed wire, and cross trenches to assault fortified enemy positions with powerful armament.

British heavy tanks are distinguished by a rhomboidal shape with a high climbing face of the track, designed to cross the wide and deep trenches prevalent on the battlefields of the Western Front.

The prototype Mark I, ready in December 1915, was called "Mother" (also known at various times as "The Wilson Machine", "Big Willie", and officially "His Majesty's Land Ship Centipede"[a]).

Mother was successfully demonstrated to the Landship Committee in early 1916; it was run around a course simulating the front including trenches, parapets, craters and barbed wire obstacles.

Col Swinton and others also did valuable work.The Mark I was a rhomboid vehicle with a low centre of gravity and long track length, able to negotiate broken ground and cross trenches.

The environment inside was extremely unpleasant; since ventilation was inadequate, the atmosphere was contaminated with poisonous carbon monoxide, fuel and oil vapours from the engine, and cordite fumes from the weapons.

[b] The side armour of 8 mm initially made them largely immune to small arms fire, but could be penetrated by the recently developed armour-piercing K bullets (introduced mid-1917).

In response, the Germans developed the 13.2 mm Mauser 1918 T-Gewehr anti-tank rifle (introduced in mid-1918), and also a Geballte Ladung ("bunched charge") – several Stielhandgranate stick grenades bundled together for a much bigger explosion.

[citation needed] A near hit by an artillery or mortar shell could cause the fuel tanks (which were placed high in the front horns of the track frames either side of the drivers' area, to allow gravity feed[citation needed]) to burst open; a direct hit by any sort of artillery shell was more than enough to penetrate the armor and destroy the vehicle.

Four of the crew, two drivers (one of whom also acted as commander; he operated the brakes, the other the primary gearbox) and two "gearsmen" (one for the secondary gears of each track) were needed to control direction and speed, the latter never more than a walking pace.

As the noise inside was deafening, the driver, after setting the primary gear box, communicated with the gearsmen with hand signals, first getting their attention by hitting the engine block with a heavy spanner.

For slight turns, the driver could use the steering tail: an enormous contraption dragged behind the tank consisting of two large wheels, each of which could be blocked by pulling a steel cable causing the whole vehicle to slide in the same direction.

There was no wireless (radio); communication with command posts was by means of two pigeons, which had their own small exit hatch in the sponsons, or by runners.

Because of the noise and vibration, early experiments had shown that radios were impractical, therefore lamps, flags, semaphore, coloured discs, and the carrier pigeons were part of the standard equipment of the various marks.

Tank Corps members were warned that poor performers would go to the front with the infantry, which the soldiers – having escaped what one described as "a horrible nightmare out of which we had just passed" – feared.

[17] Later, vertical red and white stripes were painted on the front to aid recognition after the Germans began deploying captured British tanks.

It had all its fuel stored in a single external tank, located between the rear track horns, in an attempt to improve crew safety.

The smaller sponsons could be swung inwards on hinges to reduce the width of the tank for rail transportation, where previous models had required partial disassembly to fit within the loading gauge.

Rails on the roof carried an unditching beam whose purpose was to help extricate the tank from difficult trenches by attaching it to the tracks.

It did not progress past the stage of a wooden mock-up; the project was cancelled in December 1917 in order that a tank co-developed with the US (the Mark VIII) could go forward.

The 150 hp (112 kW) Ricardo engine drove into Variable Speed Gear Ltd. pumps that in turn powered two hydraulic motors, moving one track each by means of several chains.

When Stern was removed from his post following disagreements with the War Office, he was side-lined by appointment to a new department to work on a cooperative design between the Allies – assembly in France, hulls, guns and their ammunition from the UK and other components (principally the engines) from the US.

[30] Although many broke down or became stuck, almost a third that attacked made it across no man's land, and their effect on the enemy was noted, leading to a request by the British C-in-C Douglas Haig for a thousand more.

Unfortunately for the Allies, it also gave the Germans time to develop a specifically designed anti-tank weapon for the infantry, an armour-piercing 7.92 mm K bullet.

The German army recovered about 50 abandoned British Mark IV tanks from the Cambrai battlefield and were able to restore some 30 of them to running order.

The captured tanks were painted with prominent Iron Cross emblems and a bold disruptive camouflage pattern, although some appear to have retained the original khaki colour scheme.

[32] Although some of these tanks were used in the German Spring Offensive, they tended to be deployed in small numbers for mopping-up operations,[33] while officers reported that they were unable to keep up with the fast-moving infantry.

Photographic evidence indicates that these were survivors of the Russian Civil War and had previously been displayed as a monument in Smolensk, Russia, before being brought to Berlin after the German invasion of the Soviet Union in 1941.

[citation needed] Although the first limited use of tanks in 1916 had been militarily disappointing, the first British press reports hailed them as wonder weapons, and used elaborate language to compare them to dragons, whales, dreadnoughts, crabs, mammoths or "armoured toads".

[55][56] The original 'Damon' was immobilised in a shell hole at the Battle of Ypres and served as the village war memorial until it was scrapped by the Nazis in 1941.