Website Hacked or Just Testing?

Today I was looking around for UK energy providers, and came across this home page from one of the major suppliers:

Can you see what's wrong? I don't think "hello test" should be there. It's not humorous enough to be an April Fool's Day joke, and the page footer suggests the text may have been there for a couple of weeks:

I've mentioned previously test and old pages being found by site searches, but having test content on a PLC's home page is fairly bad. What will potential new customers think? If this appeared in a company's printed brochure, would heads roll?

Was the web site hacked or was it just some poorly thought-out testing? I suspect a hacker might have added something a little bit more malicious than 'hello test' so the implication is the content was added by an authorised person. I'm worried that the live site is being used as a test platform and that content can be added without review or approval. Also, why has site monitoring not picked up on this change?

I tried to "email" the company concerned but their web form insisted I had to be a customer, so I rang a telephone number instead which again asked for an account number. I eventually got through to someone and explained the problem. It's been "passed to the IT Department". Really? Not PR or Marketing?

Don't make it difficult for people with good intentions to tell you about concerns, possible security incidents or phishing emails—help them to do it easily and quickly. You'll benefit. Why do you think food manufacturers try to encourage you to contact them about complaints, rather than leaving you to speak with your local trading standards department?

Update 14:30 hrs: No change yet—let's hope it wasn't a hacker and digital forensics are beginning.

Update 16:40 hrs: The text has been removed.