A native of County Galway a Hiberno-Norman, Lambert is described as "an officer in Lord Clanricarde's Regiment in the Duke of Ormonde's Army in Ireland 1645.
Donovan O'Sullivan more fully describes him as the secretary of Ulick Burke, 1st Marquess of Clanricarde in November 1651.
In that month, Clanricarde "dispatched his secretary, John Lambert, to Galway to find out exactly the real state of feeling in the town.
Having done this, he was to inform them that, since the Jamestown meeting had not been possible, the Lord Deputy now proposed that a Council of prelates, nobility and gentry should be held at Galway or some place near it to review the whole position, consider the possibility of foreign aids, and decide whether Clanricarde could be of any further use to the country;" (pp. 314–315).
Writing in 1820, James Hardiman included the Lamberts among the "many other families, who ... were equally ancient and respectable, as well from length of residence in the town, as through alliance with the other inhabitants, by whom they were gradually affiliated, and finally considered, without any distinction, as members of the same body" (p. 20) as the Tribes of Galway, the premier families of Galway town in the early 1600s.