Would just like to echo those saying be careful, particularly round works parties and alcohol.
18 months ago was in a similar, flirty 'relationship' with work colleague. It was great for my ego, gave me a reason to dress well for work etc, etc. Never a suggestion it would go further, both married with kids.
Actually improved my 20-year-old marriage, as I felt sexier and I had someone to talk through marital niggles.
Thought it was under control, until this year's Christmas party ... Had little contact during the do itself, but met up for walk back to tube - and out the blue - fireworks of an intensity I don't thing I've ever felt.
Now I'm totally screwed. We agreed it can never happen again, but trying to turn clock back is not working for me at least. Lost a good friend who helped me through a lot and can't help but compare my tepid sex life with what I almost had, but was never really mine to have