London Beatles guided tour?

Can anyone recommend a London guided Beatles tour?

My friends who are still in London are asking.

They looked online and there are several of them.

Some are all day, some only takes 2 hrs.

Some even requires riding around in buses.

Which one is the best?

Which one is the most informative and historically accurate?

You would think there will only be one official, Beatles approved and sanctioned tour instead of a bunch of them.

Thanks.

I did a GOOGLE search and I came up with all these just on the first result page.

That is just too confusing.

A few of these look like I would be hesitant to give them my money.

:shock:

http://www.beatletour.com/

http://www.beatlestours.co.uk/

http://www.beatlesinlondon.com/

http://www.cavernclub.org/beatlestours/item/beatles-tours

http://www.beatlesstory.com/

http://www.beatles-tours.com/

http://britmovietours.com/bookings/beatles-tour-of-london/

To save money, just make a note of these locations.

http://www.ukstudentlife.com/Britain/Music/Beatles/London.htm