For rational and honourable Labour MPs, the first objective must be to survive the planned de-selection purges. Already the Corbynites and their trade union backers have been flooding hundreds of members into their constituency parties. For the moment, despite the allurements of Lib Dems such as Vince Cable, they will probably play for time, trying to give the tricoteuse no cause to sharpen their guillotines. At some point in the next four years, however, they will have to choose between early retirement, the surrender of their brains and consciences, standing in 2020 as "Independent Labour", or flight to the Lib Dems.