the island of Anglesey in Wales , situated on the Menai Strait next to the Britannia Bridge and across the strait from Bangor . Llanfairpwllgwyngyll Welsh : Llanfairpwllgwyngyll Llanfairpwllgwyngyll shown within the United Kingdom Population 3,040 ( 2001 UK census ) Principal area Anglesey Ceremonial county Gwynedd Constituent country Wales Sovereign state United Kingdom Post