- Born: Abt 1215, West Lulworth, Wareham, Dorset, England
- Marriage: Sir William III DE MONTAGU 
- Died: After 1259, , , England
Another name for Berthe was Beota, Berta.
"Berthe (Berta), Heiress of West Lulworth
Birth: ABT 1215 in West Lulworth, Wareham, Dorset, England
Death: AFT 1259
He [William de Montagu] married Berthe, whose parentage is not known (m). He died 23 September 1270. The custody of his lands was granted to Philip Basset. [Complete Peerage IX:77, (transcribed by Dave Utzinger)]
She was heiress of West Lulworth, and was living 1259.
1. Margaret\\Margery de MONTAGU , Heir of Jenington b: ABT 1230 in Jenington, Sussex, England
2. Simon de MONTAGU b: ABT 1233 in Shepton Montagu, Wincanton, Somerset, England
3. Hawise (Helewise) de MONTAGU b: ABT 1237 in Shepton Montagu, Wincanton, Somerset, England
4. Isabel (Isabella) de MONTAGU b: ABT 1242 in Shepton Montagu, Wincanton, Somerset, England"
"VII. WILLIAM DE MONTACUTE
... By Berta his wife he left issue his son and heir, Simon. ..."
" ... After the conquest of England, the Normans built a castle on the banks of the River Frome, at the site now known as Castle Close. The castle was the focus of much fighting between the forces of Stephen and Matilda during the period of civil war in the mid 12th century. The keep was destroyed at an unknown date in the 12th or 13th century, possibly under the terms of the Treaty of Wallingford, and no visible trace remains. Up until this time Wareham had been an important port; however the growth of Poole and the gradual silting of the river caused a decline in trade and by the end of the 13th century most of the foreign trade had transferred to Poole. ..."
Berthe married Sir William III DE MONTAGU  [MRIN: 1487], son of Dreux III DE MONTAGU, "Drogo Juvenis", Baron, Knt.  and Aline BASSET . (Sir William III DE MONTAGU  was born before 1213 in Shepton Montagu, Wincanton, Somerset, England and died before 23 Sep 1270 in , , England.)