Stolen name!?!

If you're serious about protecting your name, you have to pursue the problem. Ignoring the issue is perceived (here in the US) as accepting their right to use the name. That's why the big guys (McDonalds, Nike, etc.) are so aggressive in protecting their names.

I don't have any experience with the problem you're facing, and I certainly am not a lawyer, but here's what I'd do...
1) If you haven't already registered your logo as a trademark, do so immediately. I doubt that you'll be able to get the phrase "loop card games" trademarked, as I believe the "Loop card" refers to a type of game. I could be wrong about that, of course...
2) Check if they're in the process of trademarking their name. If they are, contest it.
3) Contact them and try to straighten things out. It may be that an amicable solution is possible - linking to each other's website and so fourth.

Of these, the last is the most risky. If they've been in business longer than you have, or if they have deep pockets, or if they have aggressive lawyers, they may try to make you stop using your name.

Having said all that... It's only important if you're serious about protecting your name.

- Pat Matthews
Live Oak Games
www.liveoakgames.com

Write them immediately. Keep in mind though that trademarks, particularly unregistered common law trademarks, are limited not only by field of endeavor, but can be limited to the geographic reach of your business and its clientele.

Note also that some of your legal recourses in trademark actions may be expressly limited if you don't register your trademark. Trademark registration is a pre-requisite for certain types of legal actions.

Take note that if "Loop Card Games" is some public domain phrase describing a particular type of game, then both of you may be out of luck. Trademarks which are purely descriptive of what you sell are often deemed to be indefensible marks if they are brought to the courts. For example, if you sell cheese, you cannot trademark the word "Cheese", but you could draw a picture of a cute mouse nibbling on a bite of cheese and trademark "Cheese Brand" cheese, but even then it's probably only a defensible mark with regards to the phrase "Cheese Brand" in context with your mouse picture. Thus if "Loop Card Games" or "Loop Games" are some kind of game that is not proprietary (and instead represents a broad class of games or a public domain type of game) then only the distinctive portion of your trade name or logo is actually defensible as a mark in any case, and then the real question is whether there is any consumer confusion raised over the similarity of the defensible portion of your marks in trade.

If, as I suspect after a quick Google search, that a loop card game is not something unique to you, even if you have invented a specific type of loop card game, then only your actual logo (which is probably unique) would be a defensible trademark. In that case, the similarity of names is sort of irrelevant, because you've both effectively entered the cheese business and tried to trademark "Cheese". If that's true, then chances are that your competitor got lucky, and the trademark office in your country didn't know what the hell a "Loop Card Game" even is, and so registered the mark thinking that it was not a purely discriptive mark in trade.

The foregoing is just what I think I know about U.S. trademark law, and I can only speculate wildly whether UK law is the same.

BTW, I found both "Loop Cards Ltd." and "Loop Cards Publishing Ltd." and they might be separate companies.

Then, in the context that your company name in text form is largely descriptive, at least according to what little I know about U.S. trademark law, your company name as unadorned text may not be a protectable trademark.

Your company identity in terms of a very specific type of logo certainly is.

Make certain that the inventor of the name has not used the name in commerce. If he has, then has a clearly established trademark, because he invented the class of game and named it something that did not precede him. If he hasn't used it in commerce, then you aren't violating his trademarks, but then it's likely that your unadorned text company name is indefensible as a trademark.

To the degree that your layout is sufficiently novel (and I'd have to see the cards in full size to decide), then your card layout may constitute a defensible trade dress, which is, in and of itself, a form of mark in trade.

Like I said, most of this is based on my understanding of U.S. trademark law and I can only speculate wildly that this is applicable in the UK.

If your unadorned trademark in text form is indefensible, then if it were me (and you aren't me) I would NOT send them a cease and desist letter, but more of an advisory about what I thought might cause consumer confusion in the future.

Hope that helps.