Question: Saint Amphibalus is a venerated early Christian priest said to have converted Saint Alban to Christianity, she was offered shelter by Saint Alban in the Roman city of Verulamium, in which modern-day country?

Context articles: Nicholas Zernov
Passio Albani
Fellowship of Saint Alban and Saint Sergius
Amphibalus
Julius and Aaron
Verulamium
St. Alban's Abbey, Mainz
Germanus of Auxerre
Saint Alban
St Alban's Church, Warrington

Nicolas Michaelovich Zernov ( 9 October 1898 [O.S. 21 September] - 25 August 1980) (Cyrillic: Николай Михайлович Зернов) was a Christian Russian émigré who settled in Britain, and taught theology at Oxford University.
 He wrote many books about the Orthodox Church, and about Christianity in Russia, of which the best known is "The Russian Religious Renaissance of the Twentieth Century" (1963).
 He worked continuously for the unity of Christians, and from 1935 to 1947 was secretary of the ecumenical Fellowship of Saint Alban and Saint Sergius, which he helped to found in 1928.
The Passio Albani, or Passion of Saint Alban, is medieval hagiographic text about the martyrdom of Saint Alban, the protomartyr of Roman Britain.
 The author is anonymous, but the work is thought to have been written in the sixth or fifth century.
 In the latter case, it may actually have been authored or commissioned by Germanus of Auxerre.
 It currently survives in three different recensions and six separate manuscripts located throughout Europe, and forms the basis for all subsequent retellings of the Saint Alban martyrdom, from Gildas to Bede.
The Fellowship of Saint Alban and Saint Sergius is a Christian society founded in 1928 to foster contact between Christians, especially those of the Anglican and Orthodox traditions.
 It is named in honor of Saint Alban, the Christian protomartyr of Britain, and Saint Sergius of Radonezh, a patron saint of Russia.
 It publishes the periodical "Sobornost", edited for thirty years by Sergei Hackel, and arranges an annual conference.
 Its headquarters are currently at Oxford in Britain, and it has branches elsewhere in Britain and in Bulgaria, Denmark, Greece, Romania, Russia and Sweden.
Saint Amphibalus is a venerated early Christian priest said to have converted Saint Alban to Christianity.
 He occupied a place in British hagiography almost as revered as Saint Alban himself.
 According to many hagiographical accounts, including those of Gildas, Bede, Geoffrey of Monmouth, and Matthew of Paris, Amphibalus was a Roman Christian fleeing religious persecution under Emperor Diocletian.
 Saint Amphibalus was offered shelter by Saint Alban in the Roman city of Verulamium, in modern-day England.
 Saint Alban was so impressed with the priest's faith and teaching that he began to emulate him in worship, and eventually became a Christian himself.
 When Roman soldiers came to seize St. Amphibalus, Alban put on Amphibalus' robes and was punished in his place.
 According to Matthew Paris, after St. Alban's martyrdom, the Romans eventually caught and martyred Amphibalus as well.
Saints Aaron and Julius (or Julian) were two Celtic saints who are traditionally held to have been martyred at Caerleon, Wales, during the Diocletianic Persecution of Christians in 304.
 Along with Saints Alban and Amphibalus, they are the only named martyrs from Roman Britain.
 Their feast day was traditionally celebrated on 1 July, but it is now observed together with Saint Alban on 20 June by the Eastern Orthodox, Roman Catholic and Anglican Churches.
Verulamium was a town in Roman Britain.
 It was sited in the southwest of the modern city of St Albans in Hertfordshire, Great Britain.
 A large portion of the Roman city remains unexcavated, being now park and agricultural land, though much has been built upon (see below).
 The ancient Watling Street passed through the city.
 Much of the site and its environs is now classed as a scheduled ancient monument.
St. Alban's Abbey, Mainz (Stift St. Alban vor Mainz) originated as a Benedictine abbey, founded in 787 or 796 by Archbishop Richulf (787–813) in honour of Saint Alban of Mainz, located to the south of Mainz on the hill later called the "Albansberg".
 It was turned into a collegiate foundation ("Herrenstift") in 1442.
 The buildings were entirely destroyed in 1552, although the foundation retained a legal existence until its formal dissolution in 1802.
Germanus of Auxerre (Welsh: "Garmon Sant") (c. 378 – c. 448) was a bishop of Auxerre in Late Antique Gaul.
 He abandoned a career as a high-ranking government official to devote his formidable energy towards the promotion of the church and the protection of his 'flock' in dangerous times: personally confronting, for instance, the barbarian king, "Goar".
 In Britain he is best remembered for his journey to combat Pelagianism in or around 429 AD, and the records of this visit provide valuable information on the state of post-Roman British society.
 He also played an important part in the establishment and promotion of the Cult of Saint Alban.
 The saint was said to have revealed the story of his martyrdom to Germanus in a dream or holy vision, and Germanus ordered this to be written down for public display.
 Germanus is venerated as a saint in both the Roman Catholic and Orthodox churches, which commemorate him on 31 July.
Saint Alban ( ; Latin: "Albanus" ) is venerated as the first-recorded British Christian martyr, and he is considered to be the British protomartyr.
 Along with fellow Saints Julius and Aaron, Alban is one of three named martyrs recorded at an early date from Roman Britain ("Amphibalus" was the name given much later to the priest he was said to have been protecting).
 He is traditionally believed to have been beheaded in the Roman city of Verulamium (modern St Albans) sometime during the 3rd or 4th century, and his cult has been celebrated there since ancient times.
St Alban's Church is in Bewsey Street near to the centre of the town of Warrington, Cheshire, England.
 It is an active Roman Catholic church in the Archdiocese of Liverpool.
 The church forms part of the parish of Sacred Heart and Saint Alban.
 The church is recorded in the National Heritage List for England as a designated Grade II listed building.