Slightly stressful Sunday stroll on the beach

We nipped over to Gress beach for a walk on the beach this afternoon.

We're trying to get Hamish OK with being off the lead and coming back when we call him but it's hard going. He's fine most of the time, but then he'll see something he wants to chase and nothing will stop him, and boy is he fast! This is fine when he's chasing and jumping at seagulls, but not so good when he's chasing and jumping at toddlers. He's just being friendly as he loves to say hello to new people, but three year olds (and their parents) don't always see it that way. We try and keep him on the lead when there are people nearby, but today he chased a seagull such a long way down the beach and unfortunately that took him near to people.

He's picked up other training quite easily (sit, give a paw etc.) but coming back when we call he's just not getting - any training tips welcome!