ON THE Tory battleplan, the seat of Brentford and Isleworth, on the western fringes of inner London, was definitely supposed to turn blue on June 8th.

Like other seats in west London, it was a close win for Labour in 2015, and the Tories were confident of winning it back by a good margin. Mary Macleod, who held the seat from 2010-15, was picked to fight it again; she had to overturn a Labour majority of just over 400 votes. At the beginning of the campaign, in late April, Ruth Cadbury, the Labour MP, was clearly nervous as to whether she could hang on.

In the event, Mrs Macleod was humiliated. The election last Thursday ended with a massive 13.6% swing to Labour. Ms Cadbury romped home by 12,182 votes. It was much the same story in other west London marginals: even the Tory bastion of Kensington fell to Labour.

Tories involved in the Brentford and Isleworth campaign have spoken to The Economist to describe how it went so badly wrong. They are mainly angry and frustrated with their party's central office. As they see it, the most serious problem for local campaigners was that Conservative Central Headquarters (CCHQ) insisted on taking almost total control. In particular, staff at central office insisted that there should be no campaigning on local issues, and then tried to micro-manage local canvassing. A list of 10,000 voters was produced from CCHQ data-crunchers; these were the people whom central office had identified as the swing voters who would bring the seat back to the Tories. Local canvassers were supposed to have “10,000 conversations” with these voters, and these voters alone.

http://www.economist.com/blogs/speakerscorner/2017/06/how-tories-lost