In 1858 the new condign cathedral was opened and put under the patronage of the Virgin Mary and Saint Boniface, the latter thought to have been born in Crediton in the area of the diocese.

The cathedral is also used by Royal Navy personnel stationed at HMNB Devonport for the annual naval mass celebrated in July.

Four years later Errington was appointed coadjutor Archbishop of Westminster, and on 19 July 1855, William Vaughan from Bristol was consecrated the new Bishop of Plymouth.

[5] Work commenced on 22 June, during which a Royal Navy officer fired new Turkish Man-of-war guns in Plymouth Sound, which caused subsidence.

[8] On 26 July 1860 the Sisters of Notre Dame de Namur, who looked after poor schools, settled in the presbytery of St Mary's Church.