This date is after the TT finished. It may refer to an incident during the International cycle race which came in after the TT.
The "Whispering Death's" were often considered a right pain, they did not spend any money in cafes apart from a weak tea, and crossing the road when they were around was hazardous, if you left the pavement without looking you could easily find one parked up your posterior a-la Billy Connoly's famous joke about the bike park!
I was in Nobles during cycle race week one year, there was wholesale whinging from the competitors who slid off. At least we have leathers to protect us, sliding down the road at the Creg in lycra left quite an impression on a few of them.