Knock when pulling away and under load

[titch]

The car is a 2001 Hdi, i have just noticed a knock when pulling away, it doesn't happen all the time just if you pull away quite hard, if you are nice and gentle then it doesn't happen. The noise seems to be from the drivers side area. Had a quick look round this morning at all the suspension and can't see anything wrong had a look at the lower engine mount, seems ok there is a little movement but all the rubber looks intact and not split or perished, so looked at the top mount and it looks ok but it seems to have a fair bit of movement in it and makes a bit of a noise when you move it, have put a short video up and this was just me grabbing the plastic engine cover and rocking the engine back and forth. So what do you fellas think ?
I just hope it is the mount ( as i have a new one already to go on ) and not the captive nut underneath broken away.

Cheers Titch