UK travellers heading for the US who are in possession of passports issued in 2006, should be aware that they may not be eligible to use the Visa Waiver Programme (VWP).
As of April 1, 2016, all travellers using the VWP must have a passport "with a digital chip containing biometric information about the passport owner".
All UK passports issued after October 2006 have this chip, but ten-year passports issued between April and October 2006 will not.
The subject is being discussed on our forum here, and more details on VWP requirements can be found on the Department of Homeland Security website here.
Travellers to the US may also be intereested in another current forum string, discussing the possibility of long delays at US airports over the coming months.