An expanding door that locks away small parcels and calls the police if larger ones are stolen is on show at the CES tech expo in Las Vegas.

Its developers suggest the innovation is more secure than Amazon's own solution to the problem of parcel thieves.

It looks a bit clunky and requires a fairly large hallway, but Chris Fox tried out the invention to see if it worked in practice.

Read and watch all our CES coverage at bbc.com/ces2019