The remains of what could be one of Rome’s earliest churches have been discovered on the banks of the Tiber, close to where an epic battle between rival armies led to Christianity being adopted as the Roman Empire’s official religion.

The routine digging of a trench for an electrical cable revealed the find – a 1,600-year-old building with brick walls and exquisitely rendered floors made of red, green and honey-coloured marble from Sparta, Egypt and what is now Tunisia.

After months of excavations, archaeologists found a small cemetery with several tombs, including one with a giant amphora for a lid that contained the skeleton of a Roman man.

The splendour of the decoration, the size of the structure…