Up to now, great mirth or derision have always greeted the legend that Rome was founded on exactly 21 April in 753 BC or 2,758 years ago this month but now one of the greatest experts on the origins of Rome has come up with an astounding discovery proving that the date is about right after all.

Professor Andrea Carandini from the archaeology department of Romes La Sapienza University has unearthed in the Forum no less than the palace of what he calls the first real king of Rome, Numa Pompilius, a residence he dates back to the middle of the eighth century BC.

Usually listed as the second of the legendary Seven Kings of Rome, Numa Pompilius is held to have been a Sabine and to have ruled from 715-673 BC; he appointed the divinities of young Rome, established its first priestly order, prescribed religious ritual for them and appointed the first of the famed Vestal Virgins. Until now he has always been billed as the successor of the mythical Romulus, apparently last seen after taking a parade and being swept skywards during a dramatic storm.

As an example of the scorn heaped upon such fantasies, take this edition of The Cambridge Ancient History: The legends which grew up around the origin of Rome have so slight a value as evidence for the history of the city that they can claim little space: all that is needed to make their irrelevance plain. (Volume VII, Chapter 11).

Carandini has just shown how very wrong it is. In his tiny study at the university, as two students with folders waited outside in the corridor to see him, he disclosed he had come across the palace by chance while excavating to a depth of seven metres in the former site of the sanctuary of Vesta, which was later shifted to its present site in the Forum during the reign of Nero.

From under a pile of papers, he pulled out startlingly lifelike sketches of how the palace must have looked a sturdy, large throne room cum-banqueting hall made of thatch, timber and clay plaster, fronted by an entrance-porch upheld by two central wooden pillars and facing an ample courtyard. Inside, a low bench ran around the walls, with a gap in it for a small armchair throne. Tables for feasting were scattered around and big sacred birds were perched upon the steep, pointed roof. As you can see, it was already a house, no longer a hut, said Carandini, adding: Though I say it myself, it was a great discovery. Weve got to the very cultural and sacred heart of Rome. As a result, a whole new urban landscape is coming to light.

He has also uncovered, in the 130-metre long sanctuary, two original thatched huts which belonged to the Vestal Virgins themselves, one in which they lived and the other in which they tended the sacred flame, sometimes described as the hearth of the state. On pain of death, the six virgins were vowed to chastity for 30 years. Nobody was more surprised than me to have found their place as well as the palaceI was digging in relation to the first consuls.

He has concluded that in the seventh century BC another early king also occupied the palace namely Ancus Marcius, the traditional fourth king of Rome and the founder of Ostia. A grubby sidestreet in todays seaside resort recalls him. But what happened to the alleged third king of Rome, Tullus Hostilius, reported to be a hostile man who liked picking fights? Carandini passed him over in silence. A mystery.

Three years ago Carandini, who identified the Roman villa now ensconced within the Auditorium-Parco della Musica, also confirmed the results of a previous dig revealing, to the astonishment of all, that beneath what was thought to be the seventh-century BC foundations of the Forum, there exist still earlier ones going back to the eighth century BC. So Carandini, having found the palace, seems to have come up now with double proof of the so-called mythical date of the birth of Rome. It could amount to an archaeological revolution.

For the moment, Carandinis conclusions are not being bruited around, pending the opening of a big exhibition in the Baths of Diocletian in May. In the same month, he is to publish his findings in the bi-monthly magazine Archeologia Viva.

But how did the very month, even the day of the birthday come to be pinpointed with such fastidious scruple? We owe it to the maths of the first-century BC historian Marcus Terentius Varro. In the latest issue of Archeologia Viva, archaeologist Fabrizio Paolucci, writes that Varro probably began with the earliest certain date of Roman history, 509 BC, the beginning of the republic, and worked backwards. Calculating that each reign of the traditional seven kings must have lasted a generation and reckoning that each generation spanned 35 years on average, he simply multiplied the generations by seven and added the resulting 245 to 508: answer 753.

As for the month and day, Varro also somehow worked out that it was precisely on 21 April 753 BC that Romulus ploughed the fatal boundary around the perimeter of Rome over which his ill-fated brother Remus leapt and was then murdered.

So let no one poke fun at the date any more.