This in turn referred to the recent Sir Michael Lyle memorial lecture by Sir David Butler which you can read at
In particular, Sir David poured scorn on the record of pollsters: you can argue about details such as how many people were surprised by the hung parliament in 2010 or the Labour landslide in 1997 but there is not much room for debate that Butler was right on the overall picture when he said that ...
"It is worth remembering that unexpected results have been the norm rather than the exception. We shouldn't have been so surprised by how surprised we were this year. In twelve of the last twenty general elections the outcome has defied the prophets – and the pollsters.
- In three elections ('45, '66 and '97) there was a Labour victory of totally unexpected proportions.
- In three others ('50, '64 and October '74) an expected Labour victory was achieved by only a single-figure margin.
- In four contests ('59, '70, '92, and 2015) there was a Conservative victory that was either totally unexpected or of unexpected scale.
- And in two elections (February '74 and 2010) there was a hung parliament that few anticipated.