So in this interview on The Krotons DVD, Frazer Hines tell how he once snuck into the studio during the lunch hour and got inside one of the Daleks just to roll around in it and play pretend.
Then he heard somebody come in and he froze so he wouldn’t get told off, and it was two actors who leaned on the Dalek he was in and started bad-mouthing the show. (Not knowing he was in there.)
Partway through their conversation, Frazer rolled away going “I HEARD THAT. I’M TELLING.” in a Dalek voice.
And then apparently the two guys chased Frazer around the set going “Who’s in there?!” while he pedaled around in the Dalek prop going “YOU ARE SACKED. YOU ARE SACKED,” and waving the plunger.