The previous year had nearly destroyed him. After his coronation in 1306, Robert Bruce had been beaten at Methven, beaten again at Dalrigh, and effectively disappeared from the historical record for months on end - a king on the run rather than a king on his throne. His brothers Thomas and Alexander had tried to land at Loch Ryan and been cut to pieces by Dungal MacDouall, the Balliol partisan who controlled Galloway for King Edward I. Bruce reappeared in the spring of 1307 on the coast of Carrick, his own earldom, with soldiers recruited largely from the MacDonald-controlled Isles. He knew the country. He needed it to do the work that his depleted forces could not.

Glen Trool runs east to west, narrow and steep-walled, with a loch filling most of its floor. The path along the northern side squeezes itself against the slope before being pinched by an abutment of rock near the middle. To anyone approaching with horses and infantry, it is a textbook ambush site. Aymer de Valence, Earl of Pembroke - Bruce's own second cousin and his opponent at Methven - received intelligence that the Scottish king was camped at the head of the glen. He sent a raiding party ahead, hoping to repeat the surprise that had worked at Methven a year earlier. Bruce, watching from across the loch, had already sent men up the slope with levers and bars to loosen the granite blocks scattered along the hillside. When the English column was strung out on the Steps of Trool, he gave his signal.

The boulders went first, tumbling down a 700-metre slope onto men who had no room to scatter. Arrows followed, then Scottish soldiers charging down the hill into hand-to-hand fighting. The path was too narrow for the English to support each other from in front or behind. The cavalry had no space to manoeuvre. The numbers passed down are disputed - one account has 300 of Bruce's men defeating 1,500 heavy cavalry under Pembroke, which sounds impossibly lopsided - but the shape of the engagement is consistent: a small force using terrain to neutralise a much larger one. The surviving English withdrew. A month later, in May 1307, Pembroke tried again at Loudoun Hill and was soundly beaten there too. The Bruce who emerged from the Galloway hills had learned to fight like Wallace: ambush, surprise, advance, retreat. The throne would come.

A great lump of granite sits on the hill above the northern shore of Loch Trool now. It was placed there in 1929, on the 600th anniversary of Bruce's death, marking the spot where legend says he stood and watched the ambush unfold on the slope opposite. The stone is also the trailhead for the walk up Merrick, at 2,766 feet the highest mountain in southern Scotland. Visitors who climb up to read the inscription on Bruce's Stone often pause and look across the loch, trying to picture the Steps - the narrow path, the granite blocks waiting, the long quiet moment before the signal. Historic Scotland has the battlefield under research for formal inventory protection. Galloway has not forgotten its part in the making of a king.