THE oldest surviving tank to have seen combat marks its centenary of action this month.

The astonishing story of Tank 785 is being told at The Tank Museum in Bovington, where it has been revealed that the tank went into battle without armour.

And experts think that its crew was not told that the steel was untreated and ordinary rifle fire could penetrate it.

The Mark II tank was one of 45 summoned to take part in the Battle of Arras in France on the Western Front despite the vehicles being built solely for training purposes.

The museum’s tank was commanded by 2/Lt Herbert Chick who advanced on the enemy on May 3, 1917 with his eight-man crew.

He attacked the German lines, knocked out several machine guns and broke the wire.

However, with five of his crew wounded, two seriously, he was unable to continue the offensive.

Chick returned to allied lines and filled in a form reporting the numbers of wounded, the rounds used and the damage sustained, as well as details of the engagement.

After the Battle of Arras the Mark II tanks were gradually removed from the front as the fully armoured Mark IV tanks were rolling off the production line.

However, museum curator David Willey said that sending the unarmoured Mark IIs into battle actually helped the British war effort.

He said: “During the Battle of Arras the Germans captured a Mark II and took it back for testing.

“They realised that bullets would go straight through it and passed on this information to their soldiers.

“It was over a year before they released that the tank they had captured was only a training vehicle.

“So it was a peculiar little win for the British as it meant the Germans were a bit more relaxed about the tanks than they would have been otherwise."

“The steel had not been treated properly and while it would protect those inside against some things, rifle fire could simply pass through the armour into the interior.

“Bigger rounds and armour-piercing rounds had absolutely no difficulty in passing through.

“The bullets would then ping around inside the tank – you can only imagine the fear of Chick and his crew.

“Our research suggests that before the battle the crews were not told that the tanks were unprotected.

“Even when they must have realised this, it didn’t stop them driving at the enemy lines.

“After the battle, Chick’s tank was used as a supply vehicle and later arrived at the museum and is the oldest surviving tank ever to have seen action.

“Its damage is still visible and people always want to touch it and that really does help bring home the horrors of this war.”

The Battle of Arras was part of the spring offensive and there were just 15 Mark I tanks left from the previous year.

As they needed 60 tanks for the battle at Bullecourt the Mark IIs were summoned.

Tank 785 saw action on April 9 and then again on May 3 when it sustained the damage.

When the battle officially ended on May 16, British troops had made significant advances but had been unable to achieve a breakthrough.

Herbert Chick continued to serve and in 1918 won the Military Cross after leading his tanks into battle on foot and taking charge of the infantry.

He survived the war, changed his name officially to Chick from its original Cicognani and in 1921 married Hilda Grove. He died the following year aged 29 from a cerebral abscess. At the time he lived in Maidstone, Kent.

The Mark II tanks were built by Fosters in Lincoln.