The European Union has established common rules in all EU airports to ensure that persons with disabilities, reduced mobility or elderly (PRM) when travelling by air receive special assistance, without discrimination or any additional cost.
A free phone APP "Special Assistance PRM" is available in four languages (Italian, English, French and Spanish) and makes use of device local storage to avoid the need for data connectivity whilst travelling.
For details please see this link https://itunes.apple.com/us/app/enac-prm/id628365925?mt=8
Anybody sick of that 2 mile walk at Gatwick, just go to the Special Assistance Desk and tell them you have a bad knee. That's what I did both ways. Free ride straight to the gate, priority boarding, job done, happy days 8)