[7] In the last years of his reign, King Henry VIII of England tried to secure an alliance with Scotland by the marriage of the infant Mary, Queen of Scots, to his young son, the future Edward VI.

[8] The Earl of Angus, who is said to have arrived with monks "the professors of the Gospel", the heavy pikemen of the Lowlands, eight thousand strong, was in the lead.

[citation needed] He continued the policy of seeking forcible alliance with Scotland by demanding both the marriage of Mary to Edward, and the imposition of an Anglican Reformation on the Scottish Church.

[10] The Earl of Arran, Scottish Regent at the time, was forewarned by letters from Adam Otterburn, his representative in London, who had observed English war preparations.

[12] Somerset's army was partly composed of the traditional county levies, summoned by Commissions of Array and armed with longbow and bill as they had been at the Battle of Flodden, thirty years before.

[17] To oppose the English south of Edinburgh, the Earl of Arran had raised a large army, consisting mainly of pikemen with contingents of Highland archers.

Arran had his artillery refurbished in August, after the siege of St Andrews Castle, with new gunstocks made from woods of "Aberdagy" and Inverleith.

[8] At Monktonhall on 8 September Regent Arran made an act to protect the rights of the children and heirs of those men who would be killed fighting the English.

With Somerset's reluctant approval, Lord Grey accepted the challenge and engaged the Scots with 1,000 heavily armoured men-at-arms and 500 lighter demi-lancers, led by Jacques Granado and others.

When they broke, the English cavalry rejoined the battle following a vanguard of 300 experienced soldiers under the command of Sir John Luttrell.

[27] The English eye-witness William Patten described the slaughter inflicted on the Scots; Soon after this notable strewing of their footmen's weapons, began a pitiful sight of the dead corpses lying dispersed abroad, some their legs off, some but houghed, and left lying half-dead, some thrust quite through the body, others the arms cut off, diverse their necks half asunder, many their heads cloven, of sundry the brains pasht out, some others again their heads quite off, with other many kinds of killing.

In all which space, the dead bodies lay as thick as a man may note cattle grazing in a full replenished pasture.

The river ran all red with blood, so that in the same chase were counted, as well by some of our men that somewhat diligently did mark it as by some of them taken prisoners, that very much did lament it, to have been slain about 14 thousand.

In all this compass of ground what with weapons, arms, hands, legs, heads, blood and dead bodies, their flight might have been easily tracked to every of their three refuges.

[28]The Imperial ambassador François van der Delft went to the court of King Edward VI at Oatlands Palace to hear the news of the battle from William Paget.

Hooper's letter is undated but he includes the false early report that Mary of Guise surrendered in person to Somerset after the battle.

[31] These newsletters, though compiled and written by non-combatants days after the battle and far from the battlefield, are nevertheless important sources for the historian and for reconstruction of the events, to compare with Patten's narrative and archaeological evidence from the field.

Somerset occupied several Scottish strongholds and large parts of the Lowlands and Borders but, without peace, these garrisons became a useless drain on the Treasury.

Henry VIII had taken steps towards creating standing naval and land forces which formed the nucleus of the fleet and army that gave Somerset the victory.

However, the military historian Gervase Phillips has defended Scottish tactics, pointing out that Arran moved from his position by the Esk as a rational response to English manoeuvres by sea and land.

In his 1877 account of the battle, Major Sadleir Stoney commented that "every amateur knows that changing front in presence of an enemy is a perilous operation".

[35] Gervase Phillips maintains the defeat may be considered due to a crisis of morale after the English cavalry charge, and notes William Patten's praise of the Earl of Angus's pikemen.

[36] Merriman regards Somerset's failure to press on and capture Edinburgh and Leith as a loss of "a magnificent opportunity" and "a massive blunder" which cost him the war.

[39] William Patten mentions the Galley Subtle, captained by Richard Broke,[40] as one of the ships at the battle, and included it in one of his plans, depicted in the woodcut with its oars visible, close to Musselburgh.

[43] After the battle, Andrew Dudley and Michael Durham sailed to Broughty Castle in the Galley Subtle and fired three shots, effecting its surrender.

[45][46] William Patten described the English officers of the Ordnance after the battle retrieving 30 of the Scottish guns, which were left lying in sundry places, on Sunday 11 September.

The battle took place most probably in the cultivated ground 1⁄2 mi (800 m) south-east of Inveresk Church, just to the south of the main East Coast railway line.

[citation needed] In September 2017 the Scottish Battlefields Trust staged the first major re-enactment of the battle in the grounds of Newhailes House.

[54] David H. Caldwell has written, "English estimates put the slaughter as high as 15,000 Scots killed and 2,000 taken but the Earl of Huntly's figure of 6,000 dead is probably nearer the truth.