We are thinking of visiting my Brother who lives in England, what are (if any) the visa requirements of a US green card holder (Russian citizen) ?

Yes, a visa would be required. Here are the results I got from the Delta website:



National RUSSIAN FEDERATION (RU)
Residence U.S.A. (US)
Destination UNITED KINGDOM (GREAT BRITAIN) (GB)

UNITED KINGDOM (GREAT BRITAIN)


Passport (must be valid for the period of intended stay)
required.

Visa required. For information on minors holding Child
Visitor visas, see: For details, click here .

Minors:
children registered in parent's or guardian's passport:
- may not travel without holder of passport; and
- visa in passport (if required) must indicate that it is
also valid for the child(ren).

Flights from/to United Kingdom to/from Channel Islands,
Ireland (Rep. of) and the Isle of Man are domestic flights.
Therefore, there is no Immigration control.

Non-compliance with entry requirements(incl. forged documents)
will result in fines for carrier of GBP 2,000.- per visitor
and either deportation or indefinite delay for visitor at
point of entry (detention costs at carrier's expense).

A person may be considered committing an offence upon arrival
in the United Kingdom, if failing to produce to an Immigration
Officer a document, which satisfactorily establishes identity,
nationality, or citizenship. A person guilty of this offence
may be liable to up to 2 years in prison, or a fine, or both.

Can always get very accurate visa information no matter who you are and where you are going by clicking the following:
http://www.delta.com/planning_reservations...ation/index.jsp

Until she has her citizenship and the blue passport she is a citizen of Russia and subject to all the travel hastles that go with a red passport.

The only places she gets break having a US green card is travel to Canada, Mexico, several of the Central American countries and some of the Carribean Islands.

Thanks for all the great info.

For a stay of less than 24 hours, the UK will often allow you to clear immigration. They will write "IT" (in transit) over the stamp. (I have had many layovers in London).

If you have a green card, getting a visa to the UK shouldn't be a big deal.