Maybe you could try saying (around the house in a game like fashion for practice) "walk, walk, walk, walk, STOP" - as you say walk you and he (obviously) walk around the backyard or wherever and when you say stop you both stop like statues...then maybe he'll recognise the word when you say it and will stop?

But if he's too determined or distracted or tempted it probably won't work - so yeah, pram or lead would be the safest option.

Good luck Evie!