About 4-5 years back we found a dog wandering and managed to get him in our garden, after asking several people and OH walking around we phoned the police and were given the name of a duty kennel, the first thing they did was scan for microchip....saying it was now required....the dog wasn't. This was pre 2016 so the fines weren't in effect.
I would think in this day and age, a tag showing I am micro chipped and owner and mobile and landline are best.
P.S owner and dog were reunited.