I think "had worked" would be correct but both sound fine. To add a couple things to what Jacqui said: - I think it's a bit formal but not hugely. - If you decide to use "I left work an hour ago", it means you've left your workplace. I work from home so would use your sentence, although I'd probably omit "my". - And also, I'd probably omit the second "today".

These are all correct, but are very formal. I would change them to read: A: I left work an hour ago B: Really? How long did you work today? Did you have lunch today? A: For eight hours! I didn't, but I did eat an apple. B: You must have been hungry after eight hours! (since you're already discussing the fact that person A worked, you don't really need to bring it up again. You can, and both ways you used work fine, they're just a little more formal than most casual conversations would be.)