The rains come to Kerala for months at a time. It is the greenest state in India: hot and humid, still and brooding. The soil is so fertile that as you drift up the lotus-choked waterways, the trees close in around you, as twisting tropical fan vaults of palm and bamboo arch together in the forest canopy. Mango trees hang heavy over the fishermen’s skiffs; pepper vines creep through the fronds of the waterside papaya orchards.

In this country live a people who believe that St Thomas – the apostle of Jesus who famously refused to believe in the resurrection “until I have placed my hands in the holes left by the nails and the wound left by the spear” – came to India from Palestine after the Resurrection, and that he baptised their ancestors. Moreover, this is not a modern tradition: it has been the firm conviction of the Christians here since at least the sixth century AD.

In 594 AD, the French monastic chronicler Gregory of Tours met a wandering Greek monk who reported that, in southern India, he had met Christians who had told him about St Thomas’s missionary journey to India and who had shown him the tomb of the apostle. Over the centuries to come, almost every western traveller to southern India, from Marco Polo to the first Portuguese conquistadors, reported the same story.

The legend of St Thomas led to the first-ever recorded journey to India by an Englishman: according to the Anglo-Saxon Chronicle, King Alfred (he of the burned cakes) sent Bishop Sighelm of Sherborne “to St Thomas in India”; years later, the bishop returned, carrying with him “precious stones and the odiferous essences of that country”.

The stories that the travellers brought back with them varied little: all said how in India, St Thomas was universally believed to have arrived in AD 52 from Palestine by boat; that he had travelled down the Red Sea and across the Persian Gulf, and that he landed at the great Keralan port of Cranganore, the spice trading centre to which the Roman Red Sea merchant fleet would head each year, to buy pepper and Indian slave girls for the Mediterranean market.

In Kerala, St Thomas was said to have converted the local Brahmins with the aid of miracles and to have built seven churches. He then headed eastwards to the ancient temple town of Mylapore, now in the suburbs of Madras. There the saint was opposed by the orthodox Brahmins of the temple, and finally martyred. His followers built a tomb and monastery over his grave which, said the travellers, was now a pilgrimage centre for Muslims and Hindus, as well as Christians in southern India…..