ok, so ds is dc3. and it looks like I will finally have to babyproof the house (dd1 was passive to the point of comatose; by the time dd2 was inquisitive, dd1 was mobile, and putting gates/barriers up would have meant more accidents than they solved, iyswim. so constant vigilance was the only way)
ds is sitting in his highchair at the table. he was working hard to reach the spoon he'd had for his lunch - he wanted to chew on it.
I moved it a little further away, out of his reach, as it is a metal spoon and I don't want him biting down with newly-through tooth on the hard metal.
he reached for a bit, and clearly couldn't reach.
so he moved the table mat closer, and reached the spoon that way 
so I moved both mat and spoon a little out of his reach
he carefully measured out the distance, and then grabbed the tablecloth and yanked

thankfully there is so much crap on my table that he couldn't shift the cloth and table contents, but 10/10 for persistence to the boy.
so it looks like my days of 'move it a bit further away and hope for the best' are well and truly over - he's going to turn out to be a climber, isn't he? always into everythign I thought I had moved a safe distance away