Question: Which Cathedral is the seat of the Bishop of Portsmouth, Portsmouth Cathedral or Ely Cathedral?

full_context: Document 1: Exeter Cathedral: Exeter Cathedral, properly known as the Cathedral Church of Saint Peter at Exeter, is an Anglican cathedral, and the seat of the Bishop of Exeter, in the city of Exeter, Devon, in South West England. The present building was complete by about 1400, and has several notable features, including an early set of misericords, an astronomical clock and the longest uninterrupted vaulted ceiling in England.
Document 2: Ely Cathedral: Ely Cathedral is an Anglican cathedral in the English city of Ely, Cambridgeshire.
Document 3: Ely, Cambridgeshire: Ely ( ) is a cathedral city in Cambridgeshire, England, about 14 mi north-northeast of Cambridge and about 80 mi by road from London. Æthelthryth (also known as Etheldreda) founded an abbey at Ely in 673; the abbey was destroyed in 870 by Danish invaders and was rebuilt by Æthelwold, Bishop of Winchester, in 970. Construction of the cathedral was started in 1083 by a Norman abbot, Simeon. Alan of Walsingham's octagon, built over Ely's nave crossing between 1322 and 1328, is the "greatest individual achievement of architectural genius at Ely Cathedral", according to architectural historian Nikolaus Pevsner. Building continued until the dissolution of the abbey in 1539 during the Reformation. The cathedral was sympathetically restored between 1845 and 1870 by the architect George Gilbert Scott. As the seat of a diocese, Ely has long been considered a city; in 1974, city status was granted by royal charter.
Document 4: Dean of Portsmouth: The Dean of Portsmouth is the head ("primus inter pares" – first among equals) and chair of the chapter of canons, the ruling body of Portsmouth Cathedral. The dean and chapter are based at the "Cathedral Church of Saint Thomas of Canterbury" in Portsmouth. Before 2000 the post was designated as a provost, which was then the equivalent of a dean at most English cathedrals. The cathedral is the mother church of the Anglican Diocese of Portsmouth and seat of the Bishop of Portsmouth. The current dean is David Brindley.
Document 5: Cathedral of St John the Evangelist, Portsmouth: The Cathedral Church of St John the Evangelist (also known as St John's Cathedral) is a Roman Catholic cathedral in Portsmouth, England. It was opened in 1882 and is the first cathedral to have been built in Portsmouth. It is the mother church of the Portsmouth diocese and seat of the Bishop of Portsmouth, currently the Right Reverend Philip Egan. It was dedicated on 10 August 1882.
Document 6: Chichester Cathedral: Chichester Cathedral, formally known as the Cathedral Church of the Holy Trinity, is the seat of the Anglican Bishop of Chichester. It is located in Chichester, in Sussex, England. It was founded as a cathedral in 1075, when the seat of the bishop was moved from Selsey.
Document 7: Portsmouth Cathedral: The Cathedral Church of St Thomas of Canterbury, commonly known as Portsmouth Cathedral, is an English cathedral church. It is the cathedral of the Church of England Diocese of Portsmouth and is located in the centre of Old Portsmouth. It is the seat of the Bishop of Portsmouth.
Document 8: Diocese of Ely: The Diocese of Ely is a Church of England diocese in the Province of Canterbury. It is headed by the Bishop of Ely, who sits at Ely Cathedral in Ely. There is one suffragan (subordinate) bishop, the Bishop of Huntingdon. The diocese now covers the modern ceremonial county of Cambridgeshire (excluding the Soke of Peterborough) and western Norfolk. The diocese was created in 1109 out of part of the Diocese of Lincoln.
Document 9: Chelmsford Cathedral: Chelmsford Cathedral in the city of Chelmsford, Essex, England, is dedicated to St Mary the Virgin, St Peter and St Cedd. It became a cathedral when the Anglican Diocese of Chelmsford was created in 1914 and is the seat of the Bishop of Chelmsford.
Document 10: Dean of Ely: The position of Dean of Ely Cathedral, in East Anglia, England, in the Diocese of Ely was created in 1541 after the Dissolution of the Monasteries. The first Dean of Ely had been the last Benedictine prior of Ely.
Document 11: Newport Cathedral: Newport Cathedral (Welsh: "Eglwys Gadeiriol Casnewydd" ) is the cathedral of the Diocese of Monmouth, in the Church in Wales, and seat of the Bishop of Monmouth. Located in the city of Newport in South East Wales, its full title is Newport Cathedral of St. Woolos, King & Confessor.
Document 12: Roman Catholic Diocese of Portsmouth: The Roman Catholic Diocese of Portsmouth is a Latin Church Roman Catholic diocese that covers the Channel Islands as well as parts of England (Hampshire, the Isle of Wight and parts of Berkshire, Dorset and Oxfordshire). The episcopal see is the Portsmouth Cathedral and is headed by the Bishop of Portsmouth. The diocese is part of the metropolitan Province of Southwark, which covers all of the far South of England as well as the Channel Islands.
Document 13: Ely Eel Day: Ely Eel Day is an annual celebration observed by people from Ely, Cambridgeshire to celebrate the city's namesake — the eel. The celebrations start with a parade which begins from Cross Green outside Ely Cathedral and proceeds through the city to the Jubilee Gardens, passing by the Market Square and along the River Great Ouse at Ely's Waterside.
Document 14: Peterborough Cathedral: Peterborough Cathedral, properly the Cathedral Church of St Peter, St Paul and St Andrew – also known as Saint Peter's Cathedral in the United Kingdom – is the seat of the Anglican Bishop of Peterborough, dedicated to Saint Peter, Saint Paul and Saint Andrew, whose statues look down from the three high gables of the famous "West Front". Although it was founded in the Anglo-Saxon period, its architecture is mainly Norman, following a rebuilding in the 12th century. With Durham and Ely Cathedrals, it is one of the most important 12th-century buildings in England to have remained largely intact, despite extensions and restoration.
Document 15: Bishop of Ely: The Bishop of Ely is the ordinary of the Church of England Diocese of Ely in the Province of Canterbury. The diocese roughly covers the county of Cambridgeshire (with the exception of the Soke of Peterborough), together with a section of north-west Norfolk and has its episcopal see in the City of Ely, Cambridgeshire, where the seat is located at the Cathedral Church of the Holy Trinity. The current bishop is Stephen Conway, who signs "+Stephen Elien:" (abbreviation of the Latin adjective "Eliensis", meaning "of Ely"). The diocesan bishops now reside in Bishop's House, Ely, the former cathedral deanery. Conway became Bishop of Ely in 2010, translated from the Diocese of Salisbury where he was Bishop suffragan of Ramsbury.
ground_truth: Portsmouth Cathedral