Look at the statistic of each lap with lap-time, speed, etc. here
To analyze the record in its full beauty I created some plots:
This graph shows Tony's speed in each lap:

I did not show the first lap, he needed 23.382 seconds, which gives an average speed of 38.491 km/h.
After that starting lap he was never slower than 54.67 km/h, (# 141), the fastest lap was # 3 with 58.02 km/h. Look how he got faster towards the end of the hour. In this last lap (# 222) he averaged his second fastest speed of 57.86 km/h. The next graph shows his average speed vs. time:

I did not show the first 3 laps:
For the first lap he needed 23.382 seconds, which gives an average speed of 38.491 km/h.
For the second lap he needed 16.007 seconds (a speed of 56.225 km/h), giving 45.698 km/h. After his fantastic lap 3 (15.513 seconds, 58.01 km/h) his average speed was then 49.178 km/h. Due to his "slow" laps in the middle of the race his average speed went a little bit down (ca. 55.22 km/h), but I think he was never in danger to fall below 55 km/h.