Access chambers

A device for constructing/use as an underground access chamber or inspection chamber for a drainage system i.e. a manhole shaft, having a planar base 10 , preformed concentric walls extending from, and attached to, the base, together defining a closed bottom annular space defined between respective inner wall or form 12, outer wall or form 14 and base 10, the outer wall being tubular in form, the inner wall and the base defining an inner access chamber, the annular space being open at an end opposing the base, the inner and outer walls including corresponding inlet 16 and outlet 18 apertures receiving a sealed pipe connector, bridging the annular space, for receiving a pipe of a drainage system to which the access chamber is connected to, and connecting it to the inner access chamber, in use. Cement is poured into the annual space between the walls which sets as a annular concrete chamber wall within the forms which remain in situ. A method of use and a manhole formed using the device is also claimed. The device may be recycled plastic material.