//To reiterate, one cannot claim asylum from outside the UK.//
And to reiterate again (with apologies for the tautology), one can. One can apply for asylum in France (i.e. seek protection from harm by remaining in France). One can also do so in most of the other countries through which migrants pass to get to France. It is true that applications for asylum in the UK are not entertained from elsewhere - especially France - and that's because people in France are not under threat.
But then, of course, we're back to the old argument (which we've done to death many times over): just what is the purpose of asylum? Is it to seek shelter from harm (in which case those seeking it would normally do so in their first safe haven, as Article 31 of the UN Convention on the Treatment of Refugees suggests they should)? Or is it to roam the Continent until your destination of choice is reached? We both come up with different answers and the difference is irreconcilable.
So from my perspective, I don't know why s40 of NABA was necessary. Article 31 already provides for penalties against those who enter the UK from France without leave to do so. It is interesting to read some comments from an outfit called the "International Rescue Committee" (who have a banner on their website "Refugees Welcome"):
"Unfortunately, the Act undermines the right to seek asylum in several ways. UNHCR has said that some provisions are in breach of the Refugee Convention. They have said that powers that seek to prevent people applying for asylum, shift responsibilities for refugee protection to other states, and criminalise new arrivals, are particularly concerning."
I don't know which of the provisions are in breach of the Refugee Convention, but s40 certainly isn't. I also don't know why the UN has taken it upon itself to arbitrarily alter one of the specific terms of its own Convention, seemingly without reference to the signatories, and then say that NABA breaches that Convention. But they have.
One can only hope that the government has the will to enforce its own, recently introduced legislation. But looking at what is happening in Kent, I'm not holding my breath.