I travelled last year Nepal from US via Hethrow as permanent resident. I dod not need any transit visa. Read the following information from last part of the link I am posting here Passengers exempt from the DATV requirement Holders of certain documents are, regardless of nationality, exempt from the requirement to hold a Direct Airside Transit Visa when transiting the UK. A transit passenger is not required to hold a transit visa if he holds or a person with whom he arrives in the United Kingdom holds on his behalf: a valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel via the United Kingdom as part of a journey from another country or territory to the country in respect of which the visa is held; a valid visa for entry to Australia, Canada, New Zealand or the United States of America and a valid airline ticket for travel via the United Kingdom as part of a journey from the country in respect of which the visa is held to another country or territory; a valid airline ticket for travel via the United Kingdom as part of a journey from Australia, Canada, New Zealand or the United States of America to another country or territory, provided that the transit passenger does not seek to transit the United Kingdom on a date more than six months from the date on which he last entered Australia, Canada, New Zealand or the United States of America with a valid visa for entry to that country; a valid USA I-551 Permanent Resident Card issued on or after 21st April 1998; a valid Canadian Permanent Resident Card issued on or after 28th June 2002; a valid common format Category D visa for entry to an EEA State; a valid common format residence permit issued by an EEA State pursuant to Council Regulation (EC) No. 1030/2002; a diplomatic or service passport issued by the People’s Republic of China; or a diplomatic or official passport issued by India; or, a diplomatic or official passport issued by Vietnam. Notes: A valid U.S. immigrant visa packet (form 155A/155B)is a 'valid visa for DATV exemption purposes. An expired I-551 Permanent Resident Card issued on or after 21 April 1998 when accompanied by an I-797 letter issued by the Bureau of Citizenship authorising its extension, exempts the holder from the DATV requirement. Holding either an I-512 Parole letter or an I-797C (Notice of Action) instead of a valid U.S. visa; or a Transportation Letter instead of a valid U.S. Permanent Residence Card issued on or after 21 April 1998 does NOT qualify for exemption from the DAT visa requirement. Holding a valid travel document with a U.S. ADIT stamp worded – “Processed for I-551. TEMPORARY EVIDENCE OF LAWFUL ADMISSION FOR PERMANENT RESIDENCE VALID UNTIL…. EMPLOYMENT AUTHORIZED” does NOT qualify for exemption from the DAT visa requirement. Whether holders of non-national (including refugee travel documents) require a DATV depends on their nationality and whether they qualify for one of the exemptions listed above. So, for instance, the holder of a non-national travel document (e.g. a refugee travel document) who is a national or a citizen of one of the countries listed on the DATV list (e.g. Afghanistan) will require a direct airside transit visa if they are travelling to the UK to transit on to a third country. - http://www.ukvisas.gov.uk/servlet/Front?pagename=OpenMarket/Xcelerate/ShowPage&c=Page&cid=1020786334922 Hope this helps.