I spent six months building a bot that placed bets on the Betfair Exchange. On 29 October 2026 I stopped live betting, paused development and switched the bot off. This is what I learned, and it is mostly not about betting.

The short version: the bot's results looked good in testing, did not follow in live running, and almost every reason I found was a data or measurement error. The models were rarely the problem.

What I built

A Betfair Exchange bot across many sports: tennis, horse racing, football, darts, cricket, golf, basketball and more. It had paper trading, an optimiser that generated thousands of model variants, and live execution at small stakes (£1 to £5).…