Blyth Valley local paper's website has this news on their homepage:
Labour wins by-election
11 July 2008
By TEGAN CHAPMAN
A LABOUR party candidate has won the seat for the Croft Ward in a by-election.
Coun Deidre Campbell won the by-election yesterday.
Deirdre, who is married to Blyth Valley MP Ronnie Campbell, won the election with a 160 majority on Thursday, July 11.
Ronnie Campbell said: "It was a great victory for Labour and it was good that my wife won the by election for the Croft Ward."
Not sure what kind of byelection it is. They don't explain it. One of the 3 BV DC Croft coucillors died last April, but it doesn't seem any mention of a byelection on the council website either.
Strange - although Blyth Valley Council is a lame duck authority - it's being abolished next April to be replaced by the new Northumberland Unitary Authority.