As http://www.educationscotland.gov.uk/scotlandshistory/warsofindependence/robertbruce/index.asp - Bruce lay dying in 1329 he asked Sir James Douglas to take his heart on crusade against the enemies of Christ. Douglas carried Bruce’s heart into battle against the Moors in Spain before it was returned to Scotland and finally buried at Melrose Abbey.
On Bruce’s death his heart was cut from his body and embalmed. It was placed in a silver casket. Douglas gave land to Newbattle Abbey so that each year a mass would be sung for St Bride and 13 poor people would be fed so the saint would intercede with God for his immortal soul.
http://www.educationscotland.gov.uk/scotlandshistory/warsofindependence/blackdouglas/index.asp - Sir James Douglas and a handful of Scots knights sailed from Scotland. At Sluys in Flanders they spent 12 days aboard ships entertaining visitors. It was said that Douglas ‘bore himself magnificently, with kettledrums and trumpets, as though he had been the King of Scotland.’ The Scots ships were laden with silver vessels, flagons and dishes - their visitors were ‘feasted with two kinds of wine and two of spices.’
The Scots set sail, heading west. They landed in Spain where a stone at Santander recalled the hero ‘El Duglas’. Douglas and the Scots joined King Alfonso XI of Castile in his war against the Sultan of Granada, Muhammed IV.
In Castile an English knight marvelled at Douglas’s unscarred face - he expected the famed warrior to be covered in battle scars, as he himself was. Douglas replied, ‘God be praised, I always had my hands to defend my head.’
On 25 August 1330 Douglas and the Scots knights rode alongside the Castilians against the Moorish forces on the plain below the Castle of the Stars, at Teba. The Scots, including James Douglas, Simon Lockhart of Lee, William Keith, Robert Logan of Restalrig and Walter Logan, William Borthwick, Kenneth Moir, William St Clair of Rosslyn and John St Clair, charged into battle. The Moors feigned retreat and the Scots gave chase - leaving the Castilians behind.
When Douglas turned back he saw that Sir William St Clair was surrounded. Douglas charged to St Clair’s aid but found himself encircled. He took the silver casket containing Bruce’s heart from about his neck and threw it into the thick of the battle, shouting. ‘Now pass thou onward before us, as thou wast wont, and I will follow thee or die.’
Douglas and the Scots knights died at Teba. James’s body was found by the silver casket. Muhammed IV had the bodies of the Scots sent with guard of honour to King Alfonso. The surviving Scots, Sir William Keith and Sir Simon Lockhart, cut out their friends’ hearts and boiled their bodies down in a cauldron. They took the knights’ bones and hearts back to Scotland.
Sir William St Clair’s remains were buried at Rosslyn. The bones and embalmed heart of Sir James Douglas are buried at St Bride’s Kirk, Douglas. Robert the Bruce’s heart was buried at Melrose Abbey.
The Douglas arms changed - from the 1330s on they have borne a heart.
In the 1990s a team from Historic Scotland investigated a lead casket containing an embalmed heart found at Melrose Abbey. A stone plaque bearing the words ‘A noble hart may have nane ease gif freedom failye’ marks the spot where the heart was reburied.