A watching brief was carried out at Colchester Royal Grammar School, 6 Lexden Road, Colchester, during the construction of an extension to the science block. Planning permission for development was given with a condition for an intensive archaeological watching brief, in effect a full archaeological excavation of the new building footprint, 15 x 18m in area (CBC planning application no F/COL/04/2335). <1> A Roman temple-tomb was discovered at the site which had been constructed in the 3rd century AD at the crossroads of major routes into Roman Colchester. The ground plan of the temple-tomb was a hollow hexagon within a square. The square measured 9.2m externally, and 8.4m wall-centre to wall-centre. The hexagon was slightly uneven in size, with a maximum width of 5.2m. It had an irregular circular central space (diameter 3.0m to 3.2m). The outer wall varied in thickness from 0.86m to 0.94m. The temple-tomb survived at foundation level only, with the exception of the north wall where a course of septaria in mortar capped by a single course of dressed and externally chamfered tufa blocks gave some impression of the nature of the superstructure. Prior to the construction of the temple-tomb, a major ditch crossed the site in the 1st century AD, after which the site was used for the cremation of human remains in the 2nd century AD. Burnt patches are thought to represent the sites of pyres for the cremation of human remains, and their position in the stratified sequence indicates that this area was used for cremation prior to the construction of the temple-tomb. Evidence for earlier cremations comes in the form of loose cremated bone recovered from contexts cut through by the temple-tomb. Three other placed deposits or token burials may be associated with this phase. These are F4, a 3.25kg deposit of amphora, samian and grey ware sherds with oyster shells; F29, a possible disturbed cremation or placed deposit consisting of 0.4kg of samian and grey ware sherds; and, especially, F32, a 5kg deposit of Dressel 20 amphora sherds.