UK advert., lots of people chasing after a dog

I know a very strange request,

but has anyone seen this UK advert.? it started of with a boy and the dog, ( black and white) then somehow a lots of people chasing after a dog

when it first started it was a two parter

so has anyone seen it

thanks

Sounds like a Walkers advert, possibly?

it not walkers, It was I beleive for some big London financial company/

I think I can remember a bit more,

There some where in the countryside and the dog starts running along with the boy and a jet and there all head to london?