Downame held the rectory of Munden Magna,
Hertfordshire, from 1601. While there he published the substance of his teaching at St Paul's in successive volumes. In 1616 he was appointed Bishop of Derry. His diocese, comprising 45 parishes, was potentially valuable but in a state of decay. Little remained of the fabric of its old cathedral and 34 of its churches were ruinous or roofless. Downame's seventeen years as bishop saw the commencement and completion of Derry's new
Cathedral Church of St Columb (the first non-
Roman Catholic cathedral to be built in Western Europe) and, following his failure to agree terms with the
Irish Society for a suitable site within the city, he built a new Bishop's Palace overlooking
Lough Swilly at
Fahan. Although this was constructed on ecclesiastical land, the building costs of 2,000 marks were paid by Downame from his own private means, and in September 1634
Charles I directed Lord Deputy
Wentworth to pay Downame's widow rent for the property out of the Irish Exchequer. Downame's appointment to the See of Derry was a fitting sequel to the
Church of Ireland's adoption of its own confession of faith (the "Irish Articles") in the previous year. Although he had embraced the episcopalian tradition, his theology chimed with the Calvinist tone of the Irish Articles and he brought to Ireland a deep-seated antipathy and hostility to the
Church of Rome, which he declared had been controlled by Antichrist since the accession of
Boniface III as Pope in 607. His beliefs made him particularly acceptable to the Scots
Presbyterian settlers in Ulster and he was vehement in opposing toleration of Roman Catholic practice. He spoke the Irish Bishops' declaration of opposition when preaching before
Lord Deputy Falkland in April 1627, saying toleration made one "an accessory to superstition and idolatry and to the perdition of a seduced people". Catholic priests had a strong hold over the native population in Downame's diocese and, in despair at the civil and military authorities' acquiescence in this, he obtained from Dublin a special commission allowing him to arrest and detain all within his jurisdiction who refused obedience to him on spiritual matters. He favoured the appointment of clergy who could catechise and preach in Irish in those parishes where it was the most spoken language, and it was perhaps on such account that Fuller declared "This learned bishop was the greatest beauty [of his diocese], endeavouring by gentleness to cicurate and civilise the wild Irish, and proved very successful therein". ==Final years==