Border controls

Brian Wilson is right (Perspective, 22 May) to say that if Scotland were to introduce ­different immigration criteria to those of the rest of the UK then border controls would be an ­inevitable (if regrettable) consequence.

It is extraordinary that Humza Yousaf, who airily waved these concerns aside on television last week, is actually the minister for external affairs and international development in the current SNP administration.

Mr Yousaf appears to know little about either the Schengen Agreement or the Common Travel Area. Either he has not consulted his civil servants or has been let down by them.

It is interesting to note that Schengen itself has sometimes come under strain since its ­introduction. During the height of the Arab Spring, when many Tunisians took refuge by crossing the Mediterranean to Italy, France – which has tensions within its own north African population – came under pressure to re-introduce border controls to prevent more immigrants from the Maghreb moving to Paris or Marseilles.

Peter Lewis

Greenhill Place

Edinburgh