British producer, most known for his work with Amy Winehouse and #1 hit Uptown Funk was rumoured to work with Lana, but the collaboration sadly didn't work out.
"I hate to crap all over your excitement, but we just worked a couple [of] days together and I think she's amazing, but we didn't actually end up doing anything for her album," Ronson told Digital Spy.
"I said it and I shouldn't have opened my big mouth, but I love that track 'Honeymoon' and the stuff I've heard from the record is great."
(personally I think it was just a misunderstanding, what was said before was that Lana played ten songs from the record to Mark and he enjoyed them. But of course it's a big shame.)