It is the big white building looming over the M271 – but it is also among the greenest constructions in Britain.

Ordnance Survey’s recently-completed head office, Explorer House in Nursling, has been named one of the most sustainable buildings in the whole country.

The national mapping agency was given the Sustainable Achievement Award at a ceremony in London for the Office Agents Society Development Awards.

Around 1,000 staff members moved into the offices in Adanac Park in 2010, leaving their outdated base in Romsey Road, Southampton.

It was officially opened by the Duke of Edinburgh, currently in hospital recovering from a bladder infection, in October.

The super-efficient building, which was developed by Kier Property, has cut the organisation’s carbon footprint by 60 per cent.

Large north-facing windows cut down on the need for electric lights and the temperature of the building is strictly controlled by a finely-tuned electronic system, that opens and closes windows and controls the heating and ventilation systems.

A ground source heat pump provides the building with warmth, food waste is composted and even the toilets are flushed with harvested rainwater.