Wilf
Slouching towards Billingham
That 26% is just about the worst figure Labour has ever received, certainly since WW2. You can find a database here -Conservatives: 43% (up 2)
Labour: 26% (down 2)
Ukip: 11% (down 2)
Lib Dems: 8% (down 1)
That's pretty grim.
British voting intention opinion poll database, 1943-
I just glanced at the period leading up to the 1983 election and there were a few in the high 20s there too (think they got 28% in the actual election), but otherwise this is as bad as it gets. Different situation at the time, with the SDP/Liberal Alliance - UKIP is now the party challenging Labour - but still ultra grim.