Caputh, this doc, like many other recent ones from mainstream media are but disclosure measures to prepare mass population to the overture of knowledge about conscious life outside Earth.
A top secret Russian vehicle on a US base in the UK would cause an heck of an international incident, don't you think?
Given our earthboundness it is hard to 'proof' [though not impossible] that a vehicle is from outside Earth, but lack of reasonable explanation for thousands of cases worldwide throughout History calls for new ideas to be explored. There is nothing special about our corner of the universe. Life is abundant and concious throughout the cosmos. That is what i feel...
check this out:
http://www.youtube.com/watch?v=MoUyur4tEHAAddendum:There is a comment on this vid I tend to agree:
http://www.youtube.com/watch?v=pKHqx3y7-mk"despite the substance of this case and multiple witnesses of the highest professional caliber and who have little to gain but everything to lose, there are still those who disbelieve and try to discredit dis-info mis-info this case and the courageous individuals who have come forward to let the world know. "
I strongly recommend you or anyone seriously curious about this topic to read this book, it is not going to say they are here, but you can make up your mind in the end:

UFO Files
by David Clarke
The inside story of real-life sightings
Category: The National Archives books
Format: Paperback
Date of publication: 09 September 2009
Publisher: The National Archives
ISBN: 9781905615506
What does all this stuff about flying saucers amount to? What can it mean? What is the truth?’
Winston Churchill, Prime Minister’s Personal Minute, 28 July, 1952
The UFO Files reveals extraordinary reports by ordinary people along with details of official interest and investigations stretching back to before the First World War – for although the terms UFO and Flying Saucer were not coined until the middle of the twentieth century, people have long seen things in the sky that they could not explain.
David Clarke uncovers an array of startling stories from possible UFO reports hidden among Met Office investigations of aerial phenomena in the 1920s to the conclusions of Project Condign, the hush-hush British Intelligence UFO study completed in 2000. As well as covering Roswell and Britain’s own Rendlesham Forest mystery, Clarke raids the records for dramatic stories of abductions and close encounters, ghost aircraft and crop circles, and UFO reports by civilian aircrew and military personnel. Dramatic witness statements and interviews – many undertaken by the author himself – combine with rarely seen photographs, drawings and newly available documents to offer a unique guide to one of our most intriguing mysteries.
Contents: Introduction; 1. Strange Lights in the Skies; 2. The Flying Saucer Age; 3. Cold War UFOs; 4. Close Encounters; 5. Crop Circles and Alien Abductions; 6. Turn of the Century UFOs; Afterword.
David Clarke is Senior Lecturer in Journalism at Sheffield Hallam University. He has a long-standing interest in UFOs and other aerial phenomena, and has worked with the National Archives in promoting UFO material recently released by the Ministry of Defence. He is an experienced journalist, contributing to the Yorkshire Post and other newspapers and magazines including BBC History, as well as acting as researcher and consultant to a range of radio and television productions. He is the author of The Angel of Mons (2004).