Duncan + Robert - what happened?

I just watched this last night after having had it stored on my Freeview+ box for a while. I've not read the novel so at the end I was somewhat confused about the relationship between Duncan & Robert. Duncan sets off to go to Robert's with his suitcase, obviously with a view to moving in with him. Are we to assume that when Robert climbed into bed with Duncan in the jail cell, when he was scared of the bombing, that something sexual occurred? I am guessing it must have - or Duncan would not have felt encouraged enough to rush round to Robert's with his case - would he?