When Tennyson penned the searing words about the disastrous Charge of the Light Brigade, “Not though the soldiers knew/Some one had blundered”, he was – like the poet laureate’s angry readers – demanding answers to one of the most pressing questions of the day: what led to the slaughter?

Most of the blame has been aimed at Lord Raglan, who ordered his men to prevent the Russian army seizing the British guns, and Lord Lucan, the officer who carried out his instructions.

But more than 160 years on, a letter found among documents at the British Library written by one of the soldiers at Balaclava says the cavalry’s rank and file blamed a more junior officer.

The document has shed light on one of the British Empire’s worst military defeats, in which 107 men out of 676 were killed, 187 wounded, 50 captured, and 400 horses slaughtered.