The two principal towns in this constituency are Welwyn Garden City - the second garden city after Letchworth and which celebrated its 75th anniversary in 1995 - and Hatfield.
The constituency also takes in more rural areas including the villages of Essendon and Newgate Street and the tiny parishes of Ayot St Lawrence and Ayot St Peter. In addition there are residential developments at Welwyn and Oaklands in the north of the seat and at Welham Green and Brookmans Park in the south.
The area is socially mixed but, like most constituencies containing new towns, has a high proportion of voters living in council houses.
The constituency has tended to be a marginal for some years: it was held in the latter half of the 1970s by Labourís Helene (now Baroness) Hayman, losing it to the Tories in 1979. The abrasive Tory rightwinger David Evans held this seat from 1987, until he was beaten in 1997 by Labourís Melanie Johnson.