The Portugese royal household towards the end of the fourteenth century, while not so rich as the House of Lancaster, pursued a very anglophile policy, and, under Philippa's guidance, adopted many English customs.  The king, João I, spent most of his time in the perennial wars with Castile, leaving the day-to-day running of the country to his (English) queen, who introduced many English customs of both church and chivalry, and we might very reasonably expect that her “Mordomo-Mór” would be closely concerned in the implementation of the changes.  The role of her “Mordomo-Mór” would be very similar to a corresponding role in the English royal household, the Lord Steward or possibly the Lord Chamberlain of the Household.  Similarly the Monteiro-Mór of prince Henry, his 'great hunter', might have a role similar to that of a Chief Forester in England.  It is perhaps relevant that the suffix -Mór applied to both Mordomo and Monteiro derives from the celtic origins of the population of Portugal and is used as a superlative to denote the greatest.

To carry out his duties, James Cottrell needed to be familiar with trade, with legal affairs, with the detail of the organisation of royal feasts, with the social niceties of royal society and, this being a time of war, responsible for the keeping and control of the apparatus of war.  Philippa was also intent on the introduction of English customs into the Portuguese royal house, both religious and chivalric, and required the knightly deeds of their English ancestors it to be impressed upon her children, so that James Cottrell was required to take some responsibility for the tutoring of her sons in knightly accomplishments (including the rituals of the chase.)

Prior to the arrival of Philippa, João had a Portuguese Mordomo-Mór to run the household, Dom Lopo Dias de Sousa, who, in addition to his position in the royal household, was also a noted soldier, and the last elected Grand Master of the knightly and religious Order of Christ.  There appears to have been little conflict between Dom Lopo and James;  possibly Dom Lopo was glad to be relieved of some of his duties and the difficulty of being responsible to an English speaking queen.  If there were any difficulties, they had clearly been resolved when Lopo, son of James Cottrell, married Dona Isabel de Sousa, daughter of Gonçalo de Sousa, also connected with the royal household, and the families were united.  The marriage of their children also indicates the similar social status of their parents.

With the death of Philippa in 1415, João dispensed with the role of Mordomo-Mór for James Cottrell, who transferred into the service of Philippa's fourth (and ultimately most famous) son the Infante Dom Henrique (the Navigator), already established as João's favourite son.  The title conferred upon his earlier tutor, James Cottrell, by the Infante Dom Henrique was that of Monteiro-Mór.