Birchall said while they missed seeing Brad Pitt, they saw Channing Tatum earlier in the festival.
“I stood next to him when he watched his first bike and the look on his face was fantastic,” he said.
When Reeves arrived at the viewing point this year, Birchall found himself standing beside him as the racing unfolded.
After chatting briefly with the actor and taking a photograph with his partner, Birchall he asked if he could film him.
The resulting footage captured Reeves’ reaction to the speed and spectacle of the TT and he said the video “just went nuts”.
The clip has since amassed tens of thousands of likes and millions of views.
But it was not just Reeves’ reaction to the racing that made an impression, as Birchall described the actor as an “absolute diamond of a bloke”.
After the race, Birchall joined Reeves and his team for food and conversation behind the house.
According to Birchall, the actor remained fascinated by what he had witnessed throughout the day.
“Oh, absolutely he was, because whoever would listen, he was telling them,” he said when asked whether Reeves seemed genuinely blown away by the experience.
Despite being one of the world’s most recognisable film stars, Birchall said Reeves kept a low profile and appeared keen to avoid becoming the centre of attention.
And he added he believed Reeves’ reaction was genuine.
“It was genuine because he was talking about it for ages afterwards,” he said.