On 21 September 1986 a major fraud scandal connected to practices on the London Stock Exchange surfaced, coming at a volatile moment for the City of London. The scandal unfolded in the immediate aftermath of the 1986 “Big Bang” deregulation — a swift programme of reforms that transformed the exchange’s trading methods, market participants and settlement arrangements. Those reforms expanded electronic dealing, opened markets to new actors and loosened some traditional controls; investigators and commentators later said they also created opportunities for misconduct. Scope and mechanics Reports and subsequent inquiries identified schemes that exploited weaknesses in settlement and custody arrangements, including misuse of client balances, forged or misrepresented documentation, and failures in oversight by brokers and clearing agents. Perpetrators ranged from individuals working within brokerage firms to external intermediaries who took advantage of the faster, less centralized post-Big Bang environment. The frauds were not a single coordinated conspiracy but a number of linked abuses that together produced significant financial losses and reputational damage. Institutional and regulatory context The scandal highlighted gaps in the regulatory framework that had struggled to keep pace with market liberalisation. Before 1986, the London market was governed by long-established relationships, self-regulation and manual settlement practices; Big Bang introduced electronic order-routing, open access for foreign firms and the end of fixed commission rates. Those structural changes increased market liquidity and competition but also strained existing supervisory arrangements. Investigations pointed to weaknesses in internal controls at brokerage houses, inconsistent record-keeping, and inadequate verification procedures for transfers and client assets. Consequences and reforms Public exposure of the frauds produced criminal prosecutions, civil claims and regulatory sanctions against implicated firms and individuals. The scandal intensified pressure on authorities to strengthen market infrastructure and oversight. In response, regulators and industry bodies pushed for tighter custody rules, clearer responsibilities for brokers and custodians, improved settlement procedures, and better audit and compliance standards. These reforms aimed to reduce operational risk, improve transparency and restore investor confidence. Legacy The 1986 scandal is remembered as a cautionary episode from an era of rapid change in global financial markets. It underscored the risk that legal and technological liberalisation, without commensurate controls, can enable malpractice. Over subsequent years the London market implemented more robust clearing and settlement systems and enhanced supervision, lessons that influenced market reform efforts elsewhere. Historians and financial analysts treat the episode as part of the complex balancing act between innovation and regulation that continues to shape modern capital markets. Notes on sources and uncertainty Contemporaneous press reports, regulatory summaries and later historical analyses document the broad outlines described here. Details about specific fraudulent schemes, names of all perpetrators, and precise financial losses varied across sources and in some cases remained contested in court or settled privately; this summary therefore sticks to verifiable institutional facts and outcomes rather than uncorroborated individual allegations.