I departed a 744 recently from LHR with icy wings due high inbound fuel load.
Capt asked for deicing crew, but possibly due to comm error between he and I, he neglected to check the procedure had been actioned and pushed back without the deicing being done.
Much red faces as he returned to stand 3 mins later to have the job done - the tug crew pointed out the ice to the capt (well done chaps)
IF they hadn't noticed / realised the seriousness, could have been nasty.
That wouldn't have happened if one of the crew had popped back for a look...