When Boris Johnson edited this magazine, it proposed an amnesty for illegal immigrants — a controversial notion, but an idea he has stuck to. As London Mayor he suggested an ‘earned amnesty’: if bureaucracy had failed over many years to catch up with the 400,000 undocumented migrants in the capital, he reasoned, why not regularise their status so that they could start paying taxes and contributing to the country in other ways? When this magazine reprised the issue last week, the usual objections were recycled: why reward criminality? But the actual cases are more complicated.