can you watch TV without an aerial?

YES
Don't ask me how, but I am at Muffys Platt farm, come to set the tv up and picture come on straight away, I though that was very lucky with the dish positioning then pressed the menu button for Sat box menu and nothing happened, tried a few more and nothing, then realised the box was turned off
Checked input on tv and I was on DTV, put dish down, pulled power out of Sat box, HDMI cable out and still have picture on tv, got the 5 main channels, probably more but haven't tried,
If I take the aerial plug out it goes off, only thing I can come up with is the wire is acting as a diepole aerial, I only have a cable wired to the rear of the van where I plug my aerial into.
I have taken a video as proof

Here's the video to show TV working without an aerial - explanation anyone?

Some places all you need is a bit of wet string and you're away, as you suggest the inner aerial cable is pulling in enough.