Would this visa refusal still be relevant?

Hello,
My wife and I are, finally, about to begin the process of applying for a marriage visa.

She has been a US citizen for 6 years now, and previously held a South American passport.

In 2010 we were trying to travel from NY to Cape Town via London for the World Cup and they denied her a transit visa on the grounds that we hadn't produced enough paperwork...

Luckily she had just become a US citizen and we were able to fasttrack her passport so we were still able to travel.

The question is, is that something that needs to be stated on the spouse visa application, or does she have a clean slate, so to speak, since she is now a US citizen? It seemed like such a ridiculous thing at the time but I wouldn't want it to cause us problems or delays at this critical time.

Thanks very much in advance,
Craig

Yes, you'll need to disclose it on the application.  Include any information you may still have or just what you remember.  No including it could be considered deception and lead to a ban.  Including it will not affect anything (very common to have a prior refusal).

Hello KF, Thanks - and it's very encouraging to hear that the refusal shouldn't be too much of a problem.