WHAT Anderson had described as the ‘long and complicated inquiry’ into the Jubilee Plot finally ended on 18 November 1887 when Thomas Callan (alias Thomas Scott) was picked up in Goswell Road by a City Police sergeant as the former was coming out of a barbershop. Subsequent enquiries indicated that Callan, the last of Harkins’ known associates, had been trying for some time to cut loose from the whole operation, but his failure to dispose of nearly twenty-seven pounds of dynamite ended up sealing his – as well as Harkins's – fate. Within a few days of Callan's arrest both men had been charged with conspiracy ‘to endanger life or cause serious injury to property’ and, after a lengthy and highly publicized trial, were sentenced to fifteen years each.

Despite this apparent success, the year 1887 saw the Metropolitan Police descend into its worst crisis in more than a generation. The first real cracks appeared during the summer of 1887 when Home Secretary Matthews and Metropolitan Police Commissioner Warren found themselves at the heart of two quite separate scandals, one involving the wrongful arrest of a young seamstress for prostitution, the other the execution for murder of a possibly innocent East End salesman. Neither arguably did any widespread damage to the police's reputation, but in the fallout both the Home Secretary and the Commissioner had become legitimate opposition targets where they had previously been promising agents of change or at least honourable servants of Her Majesty's Government. Even to the moderately Liberal Lloyd's Weekly Newspaper it was now ‘becoming only too evident that under the new regime of… Mr. Matthews and Sir Charles Warren… the Metropolitan Police force is degenerating’.

Such fears were only dramatically confirmed later in the year thanks to a resurgent militancy among London's socialist and radical organizations, several of which now vied to reclaim Trafalgar Square, the site of several consequential demonstrations during the Reform agitation of the 1860s, as the unofficial headquarters of London radicalism. Besides its symbolic value, the square was also increasingly important as a refuge for many of the capital's unemployed and homeless, who, for militant socialists like John Burns and Henry Hyndman, constituted an ideal reserve army for the upcoming revolution.