Mary of Waltham was born at Bishop’s Waltham Palace on 10 October 1344 as the daughter of Edward III of England and Philippa of Hainault. Her future husband John V, Duke of Brittany was already in England as a War of Succession was going on in Brittany, and his mother had sought the support of England. He had been born in 1339 and in return for England’s support he was promised to one of Edward’s daughters.

They were officially betrothed at the age of one and five respectively. They spent most of their childhood together and must have known each other quite well. They officially married around 3 July 1361 at Woodstock Palace, and a record of wedding dress survives to this day. The tunic and mantle were made from two types of cloth of gold, and the mantle was quite long. It was lined with 600 trimmed minivers (light grey or white fur) and 40 ermine.

The couple did not immediately set out for Brittany though plans were made for their departure. Tragedy would cut married life short as Mary developed something that was described as ‘lethargic disease from which it was impossible to rouse her’. She died around 13 September 1361. Her sister Margaret also died around 1 October 1361, adding to the grief of the family. Both girls were buried in Abingdon Abbey. Though they had no children, John always remembered Mary fondly.