My husband, a corn-fed American, says “Brilliant!” all the time. I think he copped it from a beer commercial.
I don’t know WHEN Brits started saying “brilliant!” all the time, but I do know that there are a few characters in James Herriot’s All Creatures Great and Small series who say it all the time. IIRC, the surgeon in the neighboring town, whose name escapes me (he had a beautiful wife and every time Herriot went there he got snookered) said it all the time.
I’ve always said Brits have the best swears. 
The one I heard all the time (mostly from my own Brit but also in general use) is:“stunning”.
Which I rather like as I know no the difference between me and a cunning stunt 
.
And can I just add I was amazed at how much y’all really do say “Cheers”. I even heard “Cheerio” once or twice.
Bugger!
I have been watching far too many episodes of POIROT on the Bio channel, and notice Hastings constantly saying “Jolly good old chap…” - granted, these are period dramas, but every time I hear it I grin.
At one time during my teaching days in Berlin, I was the only ESL teacher that was not British…and they were always mocking my American phrases - so I am careful not to push any buttons when it comes to British/American slang/over-used phrases.
To me, however, the word “smashing” seems to emulate from all the BBC shows along with “brilliant” and “lovely”.
“Brilliant” doesn’t bother me. However, “wicked” does.
They use it the wrong way! This is an established bit of slang, so you can’t just go changing things all willy-nilly. Like its part of speech. It’s an adverb, folks. More specifically an intensive. Hell, it’s even in the dictionary as so. Adverbs need to modify something, you can’t just throw wicked out there and let it flounder. Stop making me wonder “wicked WHAT?!”
To be honest, I don’t know what exactly they mean when they say wicked. They don’t seem to mean evil, and they sure as hell don’t mean very.
Just to add to the anecdotal evidence in this thread, my English cousin first came to visit us in the U.S. in 1993, and everything was “brilliant” or “brill.” Sadly, the last couple times he came to visit in 2004, he didn’t use it as much. American slang, like “cool,” had taken over.
The last time my wife and I were in England and Ireland, “brilliant” seemed to be the standard reply of every waiter or waitress to our every meal order.
Personally, I didn’t think my lunch ordering skills were all that impressive, but I guess I was wrong.
I dunno about the English but we were using “wicked” as a superlative growing up in southern California. The waves could be wicked during a storm. I was shocked when I moved out east and New England dorks would say things like “wicked cool.” 
Aye. I bought a bottle of beer a few months back, and the girl behind the counter concluded the transaction with “Awesome!”
Now, I’m a wage slave drone, tired and wanting to pick up some booze on the way home. She is a minimum wage shop assistant probably thinking about her boyfriend or what’s happening in her university course. Let’s just effect the transaction on that basis - a guy buying a bottle of beer in a suburban liquor store. Awesome?
Like “Brilliant!”, about ten or fifteen years ago, I noticed all the Brits saying “cheers” for thanks. Then it rubbed off on the Australians a bit (I’ve done it myself), but it was really weird when an English guy asked me, “how come you lot say ‘cheers’ all the time?” I tried to explain that the Brits say it ten times for every once you’ll hear an Australian do it, but he refused to believe me. He insisted they never say it.
By golly, guv’nor. I don’t bloody well know.
When did Brits start saying “brilliant” all the time?
WAG About the time Yanks started using “absolutely” with regard to anything and everything.
“Air Head” blondes seem to be the worst offenders! :rolleyes:
I remember us having a series of Knorr ads (in the 80s?) with Keith Floyd, with the tagline “that’s Brilliant!” Were these also shown in the UK?
It’s possible usage in pervasive media like that might have reinforced things in the public conciousness.