Street Smart

Proprietary trading and the rise of casino banking: what private investors should know

Proprietary trading explained in plain English: how casino banking grew, what rules changed, and what private investors should watch.

By James Beddington · May 5, 2026

Proprietary trading sounds technical, but the idea is simple. A bank or trading firm uses its own money to bet in markets, while ordinary clients may be using the same market from the outside. That gap matters because the firm in the middle often sees more than you do.

Reviewed by James Whitfield, Senior Editor · June 8, 2026, 07:04

In this article

The Short Version

Proprietary trading means a financial firm trades for its own profit, not only for clients.
Casino banking describes the period when banks took large market bets while also holding public trust.
Rules after 2008 reduced the most obvious bank trading risks, but did not remove every conflict.
Private investors should understand who sits on the other side of a trade, especially in smaller shares.

What it means in practice

Proprietary trading is not the same as a broker placing an order for you. It is the firm trading for itself, using its own capital and taking its own risk.

That can mean buying shares, selling bonds, trading currencies, or using derivatives. A derivative is a contract whose value comes from another asset, such as a share price or interest rate.

The appeal is obvious. If a bank has smart traders, fast systems, and good information, proprietary trading can produce large profits.

The danger is just as clear. The losses sit on the same balance sheet that supports the wider business.

That balance sheet may also support client relationships, lending, market-making, and payment services. When those activities become tangled, a trading loss can become a public problem.

This is why the Street Smart lesson still matters. The issue is not that professionals trade. The issue is who carries the damage when the bet fails.

How casino banking grew before 2008

In the 1990s and 2000s, large investment banks built trading desks that acted like internal hedge funds. Hedge funds are investment partnerships that often use complex strategies and borrowed money.

Some desks made markets for clients. Others went further and took positions because the bank thought it could make money.

This is where proprietary trading became part of casino banking. The phrase is blunt, but useful. It describes banks acting less like dull utilities and more like leveraged trading houses.

Leverage means borrowed money. It can make gains look impressive, but it also makes losses arrive faster.

Before the financial crisis, some banks held huge positions in credit products. Many were tied to property loans and packaged debt.

When those markets turned, the losses did not stay neatly inside one desk. They spread through banks, clients, lenders, and then governments.

That is why the crisis changed the political argument. The public was not only watching rich traders lose money. It was watching public money protect banks that had taken private risks.

What rules changed after the crash

The United States answered with the Volcker Rule, named after former Federal Reserve chair Paul Volcker. The rule limited proprietary trading by banks that also had access to the safety net.

The Federal Reserve explains the Volcker Rule as a restriction on certain short-term trading and fund activities. In plain terms, it tried to stop banks using protected deposits as fuel for market bets.

The UK took a different route. It used ring-fencing, which separates core retail banking from riskier investment banking activities.

The Bank of England describes ring-fencing as a way to protect vital banking services. The aim is to keep current accounts and basic lending away from trading shocks.

These rules did not make banks risk-free. They changed where some risks could sit, how firms had to fund them, and how regulators watched them.

That distinction matters. A rule can reduce proprietary trading inside a bank, but it cannot remove the market instinct behind it.

Why the risk moved rather than vanished

After 2010, many traders did not leave markets. They moved to hedge funds, multi-manager platforms, and specialist trading firms.

That shift reduced one public risk. It meant fewer direct bets were sitting inside banks that also held ordinary deposits.

But it did not mean proprietary trading disappeared. It meant the same skills, systems, and incentives moved into less familiar parts of the market.

Private investors should not assume this is automatically bad. Markets need professional capital, and trading firms can add liquidity.

Liquidity means the ability to buy or sell without moving the price too much. It is useful, especially when markets are stressed.

The problem is information. A firm that trades every day may see order flow, price pressure, and client behaviour that you never see.

That is why the guide to market makers sits next to this topic. The firm quoting you a price may also be managing its own exposure.

Where private investors still feel the effect

For most private investors, the issue is not a Wall Street trading desk making a huge bet. The practical issue is the price you receive when you trade.

This is clearest in small-cap shares. These are smaller listed companies, often with fewer buyers and sellers in the market.

In those shares, the spread can be wide. The spread is the gap between the buying price and the selling price.

A wide spread means you start at a cost before the investment has moved at all. That cost often reflects risk for the market maker.

It may also reflect how much information the other side has. The old prop-trading lesson still applies because professional firms rarely trade blind.

They know when orders are thin. They know when a buyer is urgent. They know when news has not yet reached every private investor.

This does not mean every trade is unfair. It means the market is not a neutral machine built around you.

That is also why the guide to market participants is useful background. You need to know who has capital, who has information, and who has time.

A Worked Example

Suppose a small UK company announces a contract win at 7am. The headline looks positive, and the share opens higher.

A private investor sees the move and places a buy order. The quoted price is much higher than the last closing price.

The market maker is not being charitable. It is quoting a price that protects its own book if demand keeps rising or sellers appear.

A trading firm may also decide the early jump is too strong. It could sell into the move or hedge its risk elsewhere.

This is not the same as old bank proprietary trading, but the principle is related. Professional money reacts from a different position.

The private investor sees the story. The professional sees the story, the order flow, the spread, and the pressure behind the price.

That does not mean you should never trade on news. It means you should know the game you are entering before you press buy.

What This Means For You

The lesson is not that banks, hedge funds, or trading firms are always wrong. The lesson is that their incentives are not your incentives.

They may want flow, spread, speed, information, or a quick hedge. You may want a long-term investment that makes sense after costs.

Before you trade, ask who benefits from your urgency. If the answer is mainly the firm quoting the price, slow down.

Also ask whether the share is liquid enough for the size of your order. A share can look cheap until the spread and dealing cost are included.

Proprietary trading is a reminder that markets reward information and patience. Private investors rarely win by copying the speed of professionals.

They have a better chance when they understand the structure, avoid forced trades, and refuse to treat market access as market fairness.

In Plain English

Proprietary trading is when a firm trades for itself. Casino banking was the dangerous version, where big banks took market bets while still enjoying public trust.

Regulation made that harder inside banks, but it did not remove the basic market advantage professionals often hold. They still have more data, faster tools, and better sight of order flow.

For private investors, the practical lesson is simple. Do not assume the market is built to give you the same view as the person quoting the price.