By 1910, he had opened an electrical workshop in London at 15 Duncan Terrace Islington and allowed the jewel thief George Gardenstein to use his premises. On 15 January 1910, he sold oxyacetylene cutting equipment for £5 (£500 at 2013 monetary values) to George Gardenstein so that he could break into the safe at H. S. Harris jewellers Houndsditch. Gardenstein led the gang that mounted the abortive Houndsditch robbery that is the precursor to the Siege of Sidney Street. Malatesta's cutting gear is on permanent display at the City of London Police museum at Wood Street police station.