The teaser centres on a dog (because the internet loves dogs) and a child bouncing on a space hopper near some lawn furniture (because John Lewis customers like lawn furniture).
Because this is the world we live in now, John Lewis appears to have released a 10-second teaser trailer for a ~2-minute advert.
Update: Looks like Record of the Day’s tip that the song would be featured was correct.
Apparently, it wasn’t be covered by a famous musician this year (previous covers have come from Lily Allen and Tom Odell) but south London electronica trio Vaults.