No evidence that seven in ten Calais migrants are entering the UK

"7 in 10 Calais Migrants get into UK" says the Daily Mail on its front page today.

The first sentence of the article itself is less certain—"as many" as that are making it through, it says.

The article goes on to explain the source of the statistic. A few weeks ago, Kent Chief Constable Alan Pughsley told Parliament's Home Affairs Select Committee:

"Having consulted with our French colleagues, they have confirmed that through their own research, 70 per cent of migrants they process in the area of Calais leave the vicinity within a four-month period. They cannot ascertain whether these migrants leave to go elsewhere in France, or whether they enter the UK."