持中国护照，美国签证，经伦敦去美国，朋友们的答复都是需要英国过境签证，但是英国外交部网页上写的不需要签证啊，是我理解错了，还是新政策，下面是该网页的内容：Direct Airside Transit Visa (DATV) nationals - 18 November 2003
In addition to needing a visa to enter the United Kingdom nationals of the countries listed below, unless exempt, also require a visa to transit through the UK, known as Direct Airside Transit (DATV). Read our Visitors guidance for more information.
Afghanistan Liberia
Albania Macedonia
Algeria Moldova
Angola Nepal
Bangladesh Nigeria
Belarus Palestinian Authority
Burma Pakistan
Burundi Rwanda
Cameroon Senegal
China, Peoples Republic of Serbia and Montenegro
Colombia (including documents issued by
Congo, Democratic Republic the United Nations Mission
of in Kosovo)
Ecuador Sierra Leone
Eritrea Sudan
Ethiopia Somalia
Gambia Sri Lanka
Ghana Turkey
India 'Turkish Republic of Northern Cyprus'
Iran Uganda
Iraq Vietnam
Ivory Coast Zimbabwe
Lebanon
Certain exemptions to this requirement have been introduced and apply to all DATV nationals. The following categories of traveller are not required to hold a DATV and may still benefit from the Transit Without Visa (TWOV) concession:
holders of valid US/Canadian visas who also hold a ticket to or from the US/Canada routed via the UK. This will include a period of 48 hours after the expiry of the US/Canadian visa for those leaving the US or Canada to allow for those who choose to leave at the very end of the validity of their visa;
行期临近，多谢帮忙