I used to have a really close friend who happened to be someone I worked with. She joined the firm about 4 months after me and my first reaction to her was basically that I fancied the pants of her.
So I mad a bit more effort to talk to her than I perhaps would otherwise have done, flirted a little (yes i know you will all find that hard to believe) all in the hope that it would get me somewhere near to having my wicked way !
However, something strange happened, we became quite close without taking the final step of hooking up, we started seeing each other outside of work, getting to know each other, and but for the fact that we were both otherwise involved we probably would have taken the next step .
After a short time like ths I stopped wanting to sleep with her. It wasn't that I was finding her any less attractive because she is one of the hottest girls I know, and I wasn't short of feelings towards her either, in fact I loved her in a way I have never experienced either before or since.
The reason for my lose of sexual interest in her was simply that she came to mean so much to me as a friend that I couldn't bear the thought of anything spoiling it, and sleeping together would certainly have done that. I always find it a great ciontradiction that I fancied her desperatly and loved her deeply but didn't want to go any further than remain great friends.
My view though was that this friendship was special, the type that comes along once in a blue moon whereas sexual partners are so much easier to find.
So yes i believe it can work platonically and if you really are good solid friends it shgould stay that way.