From 1918, in the aftermath of both World War I and the Bolshevik revolution in Russia, British industrialists were worried about the prospect of left-wing agitators and organisers in the UK. One of the ways they fought the interests of workers was to blacklist known “troublemakers” from employment, to prevent them organising in the workplace and pour encourager les autres.

Remarkably – or perhaps not – one such blacklist survived well into the 21st century. The Consulting Association was the successor to the Economic League, which had been dissolved following a scandal in 1993. Like the League, the Consulting Association maintained a blacklist of workers, particularly in the construction industry. The list contained dossiers on thousands of people known to be members of trade unions, to have argued for better working conditions, to have reported health and safety violations, or simply to have expressed left-wing political views. It was compiled with the collusion of both trade union officials, the police, and the security services, and virtually all large employers in the construction industry checked against it when hiring workers.

In 2009 the Consulting Association was raided by the Information Commissioner’s Office, responsible for enforcing privacy and data protection laws. The subsequent revelations led to a parliamentary enquiry, the paying of millions of pounds in compensation to those who had been affected, and the passing of a law that banned employment blacklisting based on trade union membership. Despite that, the practice is still thought to continue.