It was rumoured that she became the mistress of her half first cousin Prince Edward, while she was briefly imprisoned on account of her husband's treason.
Joan de Clare (1264- after 1302), married firstly Duncan Macduff, 7th Earl of Fife by whom she had issue, and secondly Gervase Avenel.
Prince Edward
Alice was described as being very beautiful with dark hair and dark eyes. She was also flirtatious and provocative.[2] She was said to strongly resemble her grandmother Queen Isabella.[3] In the late summer of 1259, she formed a friendship with her half first cousin, Prince Edward, who would later ascend the throne as King Edward I. When civil war broke out and the barons rose up against the King led by Simon de Montfort, Alice's husband supported them. Prince Edward, who headed the Royalist Army, quickly went to war against the traitors who had betrayed his father. Tonbridge Castle, one of Gloucester's properties was captured by Prince Edward's troops and Alice, who was resident in the castle at the time, taken prisoner. It is alleged that the Prince and his cousin became lovers while she was imprisoned.[4] Edward's young wife, Eleanor of Castile was in France at the time. Alice was released shortly afterward.
At the Battle of Lewes on 14 May 1264 King Henry's forces were defeated by those led by Simon and Gloucester who commanded the second line of battle. After the victory, Gilbert and his brother Thomas were both knighted. Simon de Montfort became the de facto ruler of England. On 20 October the Earl of Gloucester was excommunicated. A month later, he fell out with Montfort and transferred his allegiance to Prince Edward. Later after the Battle of Evesham, in which Simon de Montfort was killed, Gloucester was richly rewarded for his support of Prince Edward and was granted the castle and title of Abergavenny and the castle of Brecknock. He became the most powerful lord in the Welsh Marches. In 1267, he and Alice began to live apart; on 18 July 1271 they formally separated, and the marriage was annulled on 16 May 1285. Gloucester married secondly, on 30 April 1290, Joan of Acre, daughter of Prince Edward who had acceded in 1272 as King Edward I of England. Alice died in May 1290. Through her daughter Joan, Alice was the grandmother of Isabella MacDuff, Countess of Buchan, who placed the crown of Scotland upon the head of Robert the Bruce at Scone.