Building has never been cheaper. That's exactly why validation matters more than ever.
With tools like Lovable, Bolt, and Cursor, you can go from idea to working prototype in a weekend for under £50. That also means "I built something" is no longer evidence of anything. The founders who stand out are the ones who validated the problem first.
Validation means finding evidence that real people care about the problem you're solving. Investors at pre-seed don't expect revenue. But they do expect proof that you've talked to the market, not just talked to your laptop.
A landing page is the simplest test. Put up a single page explaining the problem and what you plan to build. Add an email signup or waitlist. Drive some traffic with £50–100 of targeted ads. If 5–15% of visitors sign up, that's a healthy signal.
Surveys and interviews work, but only if you do them right. Don't ask people "would you use this?" — everyone says yes to be polite. Ask them about the problem. When did they last experience it? What did they do about it? Rob Fitzpatrick's book The Mom Test is the best guide on how to do this without accidentally getting useless answers.
If you're B2B, a signal of commercial intent is gold. That could be an email from a potential customer saying "we'd use this and here's roughly what we'd pay," or a LinkedIn exchange where someone with budget authority says "build this and we'll talk."
Fake door tests take this further. Create a "Buy Now" or "Request Access" button. Track how many people click it, then show a "coming soon, join the waitlist" message. The click-through rate tells you whether people would actually take action.
Weakest to strongest: people saying "that sounds cool" (almost worthless), email signups (mild signal), survey responses showing the problem is real and frequent (decent), landing page conversion data (good), emails expressing commercial intent (strong), actual pre-orders or deposits (strongest).
50 survey responses, 200 email signups, 3–5 customer interviews with consistent themes, or 1–2 letters of intent would be solid at idea stage. Zero evidence is a red flag. More is better, but don't let the pursuit of perfect validation become a reason not to build.
A founder who says: "I interviewed 30 potential users. 22 described the exact problem we're solving. I put up a landing page and got a 12% signup rate from cold traffic. Then I built a prototype and three of those signups converted to paying users in the first week." That founder gets meetings.
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Try the funding finder →This is general information, not financial or legal advice. Always do your own research and seek independent professional advice.