Street Smart

Inside information: the line private investors must not cross

A Street Smart explainer on inside information. What it is, why it matters, and how to interpret it as a private investor in plain terms.

By James Beddington · June 3, 2026

A sudden price fall can feel like the market knows something you do not. The Street Smart Trader reminds us that, in thinner shares, the first thing to ask is simpler: who is moving the price, and what might they be trying to do?

In this article

The Short Version

A tree shake is a sharp move that can flush out nervous sellers or attract opportunistic buyers.
The book’s Pete example is historical, but the underlying lesson about liquidity and incentives still matters.
Do not treat a sudden Level II move as automatic proof of hidden news.
Modern investors should separate company information from market structure noise.

What The Book Is Really Showing

The relevant Street Smart section follows a small-cap market maker through a volatile session. The detail is deliberately uncomfortable: the quoted price moves, the message boards light up, and traders watching the screen start inventing explanations before they have any evidence.

The useful lesson is not that every price move is a trick. It is that a quoted price is not a pure message from the company. In a thinner share, the quote can also reflect inventory, spread, order flow, liquidity and the dealer’s need to create a market.

The Historical Pete Scene

In the book, Pete is presented as a historical market-maker example from the pre-smartphone trading world. He is managing a position in a small-cap share, moving the quote lower, watching who sells, then marking the price back up as buyers appear.

That scene should be read as a dealer-side worked example, not as a current allegation about a named firm or platform. The numbers and screen behaviour belong to the book’s 2010 context. The concept that survives is the incentive problem: the person making a price may have motives that are not visible to the private investor watching the screen.

Why A Tree Shake Works

A tree shake works because it attacks confidence. A holder sees the price drop and wonders whether someone else knows something. A watcher sees the rebound and wonders whether they are missing a bargain. Both reactions can create the activity the market maker needs.

This is why the book’s sceptical City perspective matters. It asks the reader to stop treating the screen as a neutral narrator. The screen shows prices, but it does not explain motives. A falling quote may reflect bad news, thin liquidity, a wide spread, a seller in size, or a dealer trying to find the other side of a trade.

What Has Changed Since 2010

The market structure around private investors has changed since the book was first published. The London Stock Exchange still describes SETS as its flagship electronic order book, while GOV.UK’s HMRC manual describes SETSqx as combining a limited electronic order book with a quote-driven facility. The point for the reader is not to memorise market plumbing. It is to understand that different shares trade through different structures, and the screen can mean different things depending on the venue and liquidity.

The current regulatory language also matters. The FCA’s best-execution work frames execution quality around the result firms obtain for clients, including price, costs, speed and likelihood of execution. That does not make every poor fill suspicious. It does mean execution is a real obligation, not a decorative phrase.

How To Read The Screen More Calmly

The practical response is to slow the decision down. Ask whether there is a company announcement, whether volume is unusual, whether the spread has widened, and whether the share is thinly traded enough for quotes to move around without much genuine information behind them.

That is not advice to trade through volatility. It is a way to avoid mistaking pressure for evidence. If the only reason for action is that the screen has moved sharply, the book’s warning is doing its job.

A Simple Example

Imagine a small company whose shares are usually quiet. The bid drops quickly, chat rooms start speculating, and a few holders sell because they fear bad news. Then the quote reverses and short-term buyers rush in. Nothing fundamental has changed, but the price action has created its own story.

The Street Smart lesson is to separate the story from the evidence. A genuine RNS, audited results or confirmed takeover approach is information. A sudden quote move is a signal to investigate, not a reason to surrender judgement.

What This Means For You

If you invest in smaller UK shares, you are often dealing with less liquidity than the headline price suggests. That makes patience more valuable. Market orders, hurried decisions and panic exits can hand control to someone with better information about the order book.

The sensible habit is to know why you own a share before the screen starts moving. If your reason is still intact, a sharp quote move deserves investigation. If your reason was only momentum or a message-board tip, the tree shake has already found the weak branch.

In Plain English

A tree shake is the market’s way of testing who is nervous. The price move may be real, but the story you attach to it may be invented. Check the evidence before you act.