One of the earliest seeds of Christianity in England, from which the faith was destined to spread throughout the realm, was planted in what is now Oxfordshire soil. For according to the Venerable Bede, the missionary saint Birinus baptised King Cynegils of Wessex at Dorchester in 635. The former Roman stronghold then became one of the earliest Christian sites in Britain, with St Birinus establishing his cathedral here. He became the first Bishop of Dorchester, making the town a base from which to spread the word.

In undertaking missionary work in England, the Italian priest Birinus was following in the wake of St Augustine, the first Archbishop of Canterbury, who a generation earlier had been sent by Pope Gregory the Great to start converting England.

Like so many tender plants, the original bishopric had to fight to survive, flickering in and out of existence for a couple of centuries while the Danes rampaged about. But it was formally re-founded in 880 and then continued, as the centre of a diocese stretching from the Thames to the Humber, until the first Norman Bishop, Remigius, relocated to Lincoln in 1072. Oxfordshire then remained without a cathedral for 530 years — until Henry VIII, by then head of the Church of England, established his new bishopric of Oxford in 1542.

It is the sheer antiquity of Christianity that makes church-crawling so particularly rewarding in Oxfordshire. For instance, the lovely abbey at Dorchester that we see today was founded in 1140, and though not a trace of the original cathedral survives, it is nevertheless somehow apt that the great Jesse window, depicting the ancestry of Jesus, should be here of all places; for the way the churches multiplied in Oxfordshire is very like a family tree, with mother churches giving birth to daughter churches, and a complicated network of relationships developing.

But between the 10th and 12th centuries, a change occurred: our familiar parish churches began to appear. No one knows how most churches came into being, or exactly who paid for them, but by the end of the 12th century the parochial system was firmly in place. It depended on a curious mixture of ecclesiastical and lay power. All churches were controlled by the bishop but the advowson — the right to appoint a rector to the living — belonged to the landowner, which by mediaeval times might as easily have been a monastery, or an Oxford college, as a squire living in the nearby manor. The living — which was supposed to provide for the upkeep of a priest — came from tithes: namely the compulsory payment of a 10th part of all parishioners’ produce. It was paid to the rector — even though he usually appointed a vicar (from the Latin vicarius, meaning substitute), to do all the actual work. Tithe barns still exist, for instance at Great Coxwell and at Enstone. There was a building boom in the county after the Conquest, and even now many Oxfordshire churches are basically Norman, though of course nearly always — Iffley being the notable exception — overlaid for better or worse by later alterations caused by the vicissitudes of history. Wandering around churches surely provides the best possible insight into the mindset — not to mention the economic well-being or otherwise — of Oxfordshire people through the ages. For instance, the 17th-century Puritans were suspicious of the new Baroque style of the University Church in Oxford, thinking it far too Roman Catholic-looking. Yet when the Oxford Movement did indeed lead the Church of England closer to Rome in the 19th century, it was the Gothic style that was once again favoured by such architects as Scott, Pugin, Butterfield and Street, all of whom were active in the county.