How Share Prices Get Manipulated (and Why You’re Last to Know)

In which we learn how the men in dark glasses made millions from trash talk, that you can’t trust everything you read in the papers, and that London is a fertile breeding ground for insider trading.

On 19 March 2008, the share price of Halifax Bank of Scotland fell by more than 19% in a single morning. A series of alarming emails had swept through the City, from an unknown source, claiming the bank was in deep trouble and needed emergency funding from the Bank of England. The story had all the hallmarks of a credible crisis: a cancelled overseas trip by the Governor, rumours of a damaging Financial Times exposé in preparation.

All of it was completely untrue.

The Bank of England went on the record to deny the rumours — an almost unheard-of move. HBOS itself tried to reassure the markets. The panic was eventually calmed. But by then, whoever had circulated those false rumours had made, by some estimates, tens of millions of pounds by shorting the stock. The FCA’s predecessor, the FSA, investigated. Its conclusion was that “false and damaging rumours were circulating about HBOS on 19 March 2008 and these would have had some impact on HBOS’ share price.” Nobody was ever prosecuted.

How trash-and-cash works — and why it’s so hard to catch

The HBOS episode is a textbook example of what City traders call a trash-and-cash campaign. The mechanics are straightforward: you short a stock (betting its price will fall), spread plausible false information to push the price down, and close your position once you’ve made your money. The chaos you leave behind is someone else’s problem.

What makes it so difficult to prosecute is the question of evidence. A rumour passed between contacts in a Mayfair restaurant, a whisper relayed via a third party to a market reporter who includes it in good faith — where exactly does the fraud begin? In the credit crisis of 2007–2009, the waters were muddied further by the fact that the banks being targeted were genuinely vulnerable. The false rumour and the legitimate fear were almost indistinguishable.

The internet made this dramatically worse. By 2010, a mention on the Financial Times Alphaville blog was enough to light the fuse. By 2026, the same story can go from a Telegram channel to X to a national newspaper website in the time it takes to eat breakfast. The speed of transmission means that by the time the story is flagged as false, the trade has already been executed and closed.

Share ramping: the more everyday version

Not all manipulation involves elaborate City conspiracies. Share ramping — the deliberate effort to drive a share price up or down using the media — is a lot more common and a lot more mundane.

The classic ramp involves three ingredients: someone with a position in a stock, something plausible to say about it, and a route into the press. That route might be a trusted contact on a financial newswire, a broker with a good relationship with a journalist, or a company PR firm with a track record of placing bullish stories. The tip doesn’t have to be false — it just has to be timed to benefit whoever is passing it on.

The Mirror‘s City Slickers column — in which journalists Anil Bhoyrul and James Hipwell were convicted of ramping shares they personally held — is the most notorious UK example. But it happened in 2000. What’s changed since then is the platform. The same dynamic now plays out on Reddit threads, Discord servers, and Telegram channels where anonymous accounts build followings, talk up small-cap stocks to their audience, and disappear once the price has moved.

The journalist’s filter — and why you should use it too

Ian Lyall spent fifteen years as a City journalist, including as investment editor and City news editor of the Daily Mail during the banking crisis. His account of the tip-off calls a good stock market reporter receives every day is instructive — not because it’s exotic, but because it’s so ordinary.

A market maker calling with bullish news on a small mining stock. A Monaco-based businessman flagging a rumoured bid on a FTSE 100 insurer. A broker hinting at forthcoming clinical trial data from a drugs company client. Each call requires the same two questions: Does the story make sense? Do I trust the source?

What’s striking is how often the answer to both questions is no — and yet the story runs anyway, wrapped in enough qualifications to be technically defensible. This is not always dishonesty. Sometimes it’s deadline pressure, sometimes it’s the journalist being genuinely misled, and sometimes it’s the information ecosystem doing what it was designed to do.

The lesson for the independent investor is to apply the same filter. Not every bullish story about a company you hold is a pump. But the ones that come from nowhere, lack specific detail, involve a stock with thin trading volume, and appear across multiple outlets simultaneously — those deserve a great deal of scepticism.

London’s insider dealing problem

Here is a statistic that should concentrate the mind. According to FCA data, suspicious share price movements precede almost one third of all takeover announcements in Britain. In America, that figure is far lower — not because American companies are more virtuous, but because American regulators are more aggressive.

When Ian Lyall wrote this book in 2010, the FSA had brought exactly one successful criminal insider trading prosecution since 2001. The FCA, which replaced the FSA in 2013, has done considerably better — Operation Tabernula alone resulted in multiple convictions, and several high-profile cases have followed. But compare this with the United States, where the Department of Justice and SEC process dozens of insider trading cases every year, impose nine-figure penalties, and send people to prison for years.

In the UK, the biggest financial penalty for insider dealing at the time the book was written was £750,000. In America, Joseph Nacchio — chief executive of communications group Qwest — was fined $19 million, forced to forfeit $52 million in illegal gains, and jailed for six years. The message sent by the two regulatory environments is very different.

What this means in practice

The City has always run on networks. Networks of trust, of favours owed, of lunch debts and whispers. That is not always corrupt — much of it is simply how any close-knit professional community functions. But it does mean that price-sensitive information about deals, earnings surprises, and regulatory decisions seeps through those networks long before it reaches a public announcement. And as an independent investor sitting in front of a screen, you are almost certainly at the end of that chain.

This doesn’t mean research is pointless. It means you should understand what research can and cannot tell you. A company’s fundamentals might be strong. Its management might be honest. Its market position might be excellent. And its share price might still move sharply before an announcement — not because the market is efficient, but because someone in a Mayfair office knew something before you did.

Forewarned is forearmed. The City is not designed to be your enemy. But it is not designed to be your friend, either.

Street Smart is a series drawn from first-hand experience of UK financial markets. Each post takes a chapter from the City’s history and asks what it still tells us today.

This post is drawn from The Street Smart Trader by Ian Lyall. Republished with permission.

This article is for informational purposes only and does not constitute financial advice. Investment values can go down as well as up. Always do your own research before making any financial decisions.