The group's revenue predominantly arises from the provision of services within the United Kingdom, with less than one per cent of external revenue and non-current assets being overseas.

The group has a large and diverse domestic retail customer base with no significant reliance on any single customer in this area. Following the sale of the group's non-household business on 1 June 2016 (see note 9), £402.7 million (2016: £nil) of the group's revenue from wholesale water and wastewater services during the year was derived from sales to Water Plus Group Limited (Water Plus), a joint venture formed during the year between United Utilities PLC and Severn Trent PLC, and its subsidiaries. Please see notes A4 and A6 for further details.

The board of directors of United Utilities Group PLC (the board) is provided with information on a single segment basis for the purposes of assessing performance and allocating resources. The board reviews revenue, underlying operating profit, operating profit, assets and liabilities, regulatory capital expenditure and regulatory capital value (RCV) gearing at a consolidated level. In light of this, the group has a single segment for financial reporting purposes and therefore no further detailed segmental information is provided in this note.