The boxes arrive at Welwyn Hatfieldpublished at 22:55 British Summer Time 4 July
Amy Holmes
Political reporter, BBC Three Counties
This seat was created in 1974, and it has been served by both Labour and Conservative MPs, although it has been Tory since 2005.
In those 19 years, the MP has been the current Defence Secretary, Grant Shapps, but there's a strong suggestion he may be one of the Conservatives that loses their seat.
The constituency is split into three parts: Labour tends to do well in Hatfield, while Welwyn Garden City is stronger for the Tories, and then there’s Welwyn Village/Brookmans Park, which is also seen as a strong area for Conservative voters.