7 Rules Every Private Investor Should Know

There is an old saying among professional traders that somewhere in every trade, there is a fool. The professional’s job is to make sure that fool is not them. This is not cynical, exactly. It is just an honest description of how markets work. The City of London is a place where information, capital, and connections are distributed very unequally, and that inequality shapes every trade that happens within it. Understanding where you sit in that food chain is the first step toward not being at the bottom of it.

Monty has been working in the City since he left school at 17. For a decade he ran one of London’s biggest dealing rooms. The rules he lives by have been refined over more than 30 years of watching what happens to traders who ignore them. They are not complicated. But they are honest about something that most investment books prefer to gloss over: the private investor starts at a structural disadvantage, and the first thing to do is understand exactly what that disadvantage looks like.

The first rule is that information is not evenly shared. When a professional trader arrives at their desk in the morning, they are sitting in front of a bank of screens showing live prices, rolling news feeds, analyst commentary, and real-time order flow. The average retail investor sees a delayed price quote and whatever appeared in the financial press since yesterday. That gap has narrowed considerably since the internet arrived, but it has not closed. Professionals also have networks: analysts, fund managers, sales desks, journalists. The independent investor, by definition, does not.

The second rule is that the costs of trading are not equal. A dealing room operating at scale can execute large transactions at a fraction of what a retail stockbroker charges. A flat fee of £9.95 sounds cheap, but trading costs are only part of it. There is the bid-ask spread: you buy at the offer and sell at the bid, and the gap between them is a built-in loss on every trade. There is the potential delay between placing your order and its execution. And professionals trading in size can engineer better prices in ways that are simply not available to private investors.

The third rule is that position size matters in ways that go beyond the obvious. Professionals trading with large pools of capital can create momentum. A fund buying heavily into a stock moves the price. A private investor buying at the same time benefits from that movement without causing it. Position size also determines options: a professional sitting on a loss can average down, buy time, or use derivatives to hedge. An individual with a fixed pot of savings has none of those levers available.

The fourth rule is that it is not what you know, it is who you know. The City operates on a network that has existed for centuries and that passes information, in entirely legal ways, between people in close contact with each other. A fund manager calling a company’s investor relations desk, a research analyst speaking to a supply chain contact, a trader picking up market gossip from a counterpart: none of this is insider dealing, but all of it gives those in the loop an advantage that a private investor at home cannot replicate.

The fifth rule is to be dispassionate. Professionals are not less emotional than anyone else, but they learn to compartmentalise. A losing trade is a problem to be solved, not a source of distress. Monty describes thinking in ticks and bars rather than pounds and pence. That abstraction is a coping mechanism, but it is also a competitive tool. Private investors who think in terms of how much of their savings they have lost are far more likely to make decisions driven by fear or pride rather than any rational assessment of the position.

The sixth rule concerns risk and resources. Professional traders will sometimes double down on a losing position because they have the capital to sustain the bet and the experience to judge that the position will recover. This is not recklessness: it is a calculated use of resources and knowledge built over years. For a private investor with limited capital, averaging down on a falling stock is considerably more dangerous. It can turn a manageable loss into a serious one. The rule is not to copy what professionals do, but to understand why they do it before deciding whether any of it applies to your own situation.

The seventh rule is perhaps the most important, and the one most at odds with the instinct to trade actively. The private investor’s structural advantages over the professional are not obvious, but they exist. You do not have a compliance officer scrutinising your positions. You do not have a quarterly performance target to hit. You are not under pressure to be seen to be doing something with the money. The one weapon the private investor has that the professional does not is time. As Justin Urquhart Stewart, co-founder of Seven Investment Management, puts it: “It is time in the market, not timing the market, that makes people rich.” Holding a diversified portfolio for the long term does not make headlines. But the evidence for it is overwhelming.

The instinct, when reading these seven rules, is to assume the lesson is to try harder: to get better data, to trade more cleverly, to find the edge the professionals have missed. That is the wrong reading. The rules exist to explain why competing with professionals on their own terms, at their own pace, in their own market, is a losing game for the private investor. The lesson is not to get better at that game. It is to stop playing it altogether.

The private investor who uses a stocks and shares ISA, builds a diversified portfolio of low-cost funds, and contributes steadily over decades is not losing to the City. They are operating on a completely different timescale. The dealing room trades in seconds, minutes, and quarters. The private investor’s edge is measured in years and decades, and on that timescale, most of what makes the professional powerful simply does not apply. Patience, discipline, and the consistent use of tax-efficient wrappers are not consolation prizes. They are genuine competitive advantages, and they are advantages that compound over time in a way that no amount of clever short-term trading can match.

Before you place your next trade, work through these seven rules and ask honestly which ones you have internalised. Most private investors acknowledge the information gap and the cost disadvantage, but underestimate the importance of emotional discipline and the value of time. If you are trading frequently, reacting to news, or trying to anticipate market moves, you are competing on ground where the professionals will almost always win. The private investor’s edge lies elsewhere. Find it there, and use it consistently.

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

Street Smart is a series drawn from first-hand experience of the City of London, updated as each new chapter arrives.

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.