This whole "telegraphing your punches" argument is a red herring.

We MUST set an exit date, or those responsible for securing the country AFTER we leave will not step up. It's not like it's a huge secret that we're GOING to with draw, and a fixed timetable is in our national interests for multiple reasons.
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The charm of fishing is that it is the pursuit of what is elusive but attainable, a perpetual series of occasions for hope. -John Buchan