Bittern, Very Fast Steam Loco - 91.5 MPH. 

LNER A4 Class 4464 (60019) "Bittern" has been given dispensation to run at 90MPH on the East Coast Main Line on June 29th 2013, in exactly 1 month, to celebrate the 75th Anniversary of Mallard's world speed record, subject to a satisfactory high speed test. This is that test. The weather was perfect - damp, cool, no wind. Bittern left Didcot at 05:23 am and flew through Slough 05:58 at full pelt for an average of 60mph over the 35 miles. The 6.2 mile section between Maidenhead and Slough was completed in 4 minutes, an average of 93MPH. Using film time markers I timed the whole train at 90mph through Taplow where this film was shot.
Edit 15th Jan 2014: I have just found out that official on-board timing had this train clocked at 91.5mph through Taplow. A DVD of the the story of Bitterns modern high speed passenger run can be purchased at www.ovpsteam.co...