When Darwin gets out, or off his lead. This is what we do.
Before you run out grab a tin of tuna or something you know should tempt them.
Once you have them in sight DON'T chase them.
It's a game they'll let you get close enough then run off again.
Call to them to get their attention, shout whatever you normally say when you're going to feed them
That definitely grabs their attention.
Then simply sit down on the ground and pretend to eat whatever is is you brought with you.
They should then come running over to see what it is you've got for them to eat.
wave the treat / food around a bit so they get the scent then slowly reach out and take hold of their collar when they are close enough.