Yamamoto plans to talk with Senna

The 28-year-old, who is set to make the 15th start of his Formula 1 career, admitted that he did not expect to have receive the call to step up from test driver status at Silverstone on Thursday, after Senna was dropped without explanation by the Spanish team for the event.

"I was really surprised," Yamamoto told AUTOSPORT. "Normally when you get news that you are driving, as a driver you are very happy.

"But it was too surprising that I was a bit shocked.

"I had to adapt quickly and concentrate for this weekend, and gather any information that I could. It wasn't an easy day yesterday, but I worked with the mechanics, engineers and team members and slowly we could prepare everything for this morning. I was ready this morning."

The Japanese former Jordan, Super Aguri and Spyker driver admitted that the situation had made things awkward between himself and Senna and that he intended to speak to the 26-year-old, who had started the first nine races of the season for HRT.

"Actually we have said 'hi', but I understand how he feels as a racing driver and I want to talk him a bit later on when things have calmed down a bit," said Yamamoto. "At this moment it is very hard to speak to each other, I believe.

"It is a bit of strange circumstances, but personally we have had good relations since I joined this team. He was always nice, and that's why... I don't know what he thinks, but I want to speak with him later on."

Yamamoto ended the day 23rd fastest, more than a second away from his team-mate Karun Chandhok and admitted that he still needed more time to reacclimatise to the car and the soft slick Bridgestone tyres - which he has not used before.

"I am happy with what we achieved today, but still I know I need to improve in a lot of areas," said Yamamoto. "Especially the prime tyre was okay, but when we switched to the soft option tyre we lost a lot of time compared to Karun.

"This definitely comes from [a lack of] experience because I never drove on these kind of slick tyres. Still we are in middle of the weekend so I just have to look forward and keep going step-by-step."