Novelty is lost, not stolen

A patent in the UK and at the European Patent Office is only granted for an invention that is new at the date of filing. New means it has not been made available to the public anywhere, in any form, by anyone — including by the inventor. The most common way a good invention becomes unpatentable is that its owner described it before the application went in.

That description does not need to be complete, or published in a journal. A demonstration at a trade show, a slide in a fundraising deck circulated without confidentiality, a product listing, a thesis in a university library or a detailed answer on a forum can all be enough if they teach someone skilled in the field how the invention works.

The grace period that mostly does not exist

The United States gives inventors twelve months after their own disclosure to file. Europe and the UK do not. Relying on the American grace period is a decision to give up protection across Europe, and it is usually made without anyone noticing it was a decision at all.

File first, then talk

A first UK application can be filed quickly and cheaply, and it fixes a priority date. From that date you have twelve months to extend protection abroad, and you can talk about the invention in the meantime. Where a conversation cannot wait, a properly drafted confidentiality agreement keeps the disclosure out of the public domain — but it must be signed before the conversation, not after it.