The structure has been made by wasps and in the past we have come across the same type of nest on our front door casing and on the window casings. We blogged about them here.
Our friend and insect expert Tim commented on these saying: "These are not your normal wasps and do not need to be removed... this is as large as this nest gets! They are a semi-social hunting wasp Polistes gallicus or similar... they are called "paper wasps". They build a 'communal' nest. Each cell is filled with caterpillar [paralyzed] upon which the egg is laid. Each wasp is a female and adds as many cells to the nest as she has eggs. I've handled these without getting stung..."
Perhaps these are 'Traveler Wasps' and wanted something more mobile!!
