A British artist who risked his life to draw intricate sketches of enemy front lines during the First World War was finally unmasked yesterday more than 30 years after his death.

Len Smith, a sapper and espionage expert with the Royal Engineers Special Branch, would hide in no man's land for days on end, sketching enemy positions with remarkable accuracy. Now a book of Sapper Smith's drawings has been released to the public. Armed with little more than a set of coloured pencils Mr Smith, who was from Essex, returned to no man's land day after day to create drawings of German troop positions.

In one of the most astonishing feats of counter-espionage Mr Smith crawled within metres of an enemy HQ and drew a battle-scarred tree so accurately that on his return to the trenches British Army chiefs were able to recreate a perfect, hollow steel replica. Without the Germans knowing, sappers replaced the real tree with the replica one in the dead of night. Tunnels were soon dug towards the steel hull, enabling soldiers to listen in on German positions night after night undetected.