Drogo was a `friend of the family' of William the Conqueror .

From the Domesday book , Somerset, 45,12 (written around 1080):

The original reads Drogo de Montagud with the name written vertically, that is, the last name is above the first and they both share the same D.

Also of interest, Drogo is not the only Montacute on the page. The Domesday book, Somerset, 45,18, describes Drogo's brother Ansger as follows:

The original reads Ansgervs de Montagud. Ansger de Montaigu was one of Williams 'companions' , that is, officers.

Drogo de Montagud also owned lands in Devon. From the Domesday book, Devon, 15,23-24:

In the Falaise Roll, Crispin and Macary describe the brothers Drogo and Ansger as follows:

"From the parish of Montaigu-les-Bois, in the arrondissement of Coutances, commune of Gavay. Ansger de Montaigu, with his brother Dreu, came to England at the conquest in the train of the earl of Mortain. The former (Ansger, ed.) held lands-in-chief in the counties of Devon and Somerset, and as an under-tenant of the count of Mortain in Dorset, and of the bishop of Countances in the same county. It is apparent that he died without posterity, as there is no record of any in England. Dreu, his brother, held several manors in Somerset, among which were Shipton and Sutton. The first was his seat, which was later called Shepton-Montague, and the latter was designated Sutton-Montague. He was the father of William de Montagu, who succeeded him towards the end of the reign of Henry I. He left much posterity in England, among whom were the earls of Salisbury and Manchester. The name appears on the Dives roll, as well as that of Leland." (Crispin and Macary)

Robert de Montacute was a senior witness to the charters for the abbeys of Dunfermline and Holyrood by King David of Scotland. In The Anglo-Norman Era in Scottish History, Barrow notes:

"... suggesting once again a Somerset link with the Scottish court... It may not be fanciful to envisage these west country lords traveling north to prospect the possibilities of future settlement not so much on their own behalf as on behalf of their followers and dependents...

Robert de Montagu was presumably a younger son of Drogo de Montagu... a William son of Robert de Montagu appears in 1198... It may be noted that a gift to Bruton by Henry Lovel was made for the soul of the younger Drogo de Montagu."(Barrow)

Henry Lovel was the son of a Ralph Lovel that was among those who encouraged King David of Scotland to invade England in 1138.

Norman and Viking history seems quite disjoint. To understand these times, it also helps to study feudalism [1] .

A hide is a unit of land measurement, usually considered 120 acres. One has to be careful, since in early times the exact measurement of land was not considered important, but rather how hard it was to work.

A virgata is a unit of land measurement, usually considered 30 acres, that is, 1/4 of a hide.

Sources:
The Domesday Book.
The Anglo-Norman Era in Scottish History, G.W.S. Barrow.
Falaise Roll Recording Prominent Companions of William Duke of Normandy at the Conquest of England, Crispin and Macary.

http://www.montaguemillennium.com/familyresearch/h_1066_drogo.htm