From EADT24:

THE final piece in the archaeological jigsaw that is Colchester's Roman Circus has been found by excavators, the EADT can reveal.

The location of the 12 gates that released the competitors into frenetic and often violent chariot races was discovered near the sergeants' mess building in the former Colchester Garrison at Abbey Field.

These would have operated in the same way as greyhound traps, unleashing the charioteers on to the quarter-mile long opening stretch of the track.

With four horses at the head of each chariot, on full races there would have been 48 steeds pounding around the circuit, which is the only one ever to be found in the UK.

Foundations of the circus were first located in late 2004 when archaeologists were conducting digs at Abbey Field, prior to the construction of new housing.

News of the discovery was reported by media organisations around the world and thousands of visitors flocked to see the remains.

Since then, archaeologists have painstakingly discovered the stands, the central barrier and even one of the two turning posts round which the charioteers would career at the far end of the circus.

Now, with the discovery of the gates, a small piece of every constituent part of the circus has been located.

Developer Taylor Woodrow has supported the work of volunteers from Colchester Archaeological Trust (CAT), while their recent dig to find the gates was funded partly by the Essex Heritage Trust and also the Corporate Friends of the Friends of CAT.

Yesterday Philip Crummy, director of the trust, said that debris had even been found of the box which would have been above the gates, from where a magistrate would have dropped a handkerchief to herald the beginning of the seven-lap race.

A second magistrate would then have opened the traps with a lever and the chariots would thunder out to begin the spectacular competition.

“We know the box had a nice roof and painted walls, because when the circus was demolished - probably in the late Roman period - they left bits of them on the ground,” Mr Crummy said.

“This find is an important step forward for us. We are highly delighted. Although we have only excavated small parts of the site, we have now got all the elements of the circus.”

There's a good (illustrated) excerpt from William Smith's Dictionary at Lacus Curtius ... scroll down to the section on carceres for an explanation of how these 'gates' might have worked ...