Usain Bolt has insisted that he will not know if he is fully fit until he races at the Anniversary Games on Friday night.

The world and Olympic champion has struggled with injury during the 2015 campaign, but the Jamaican is hoping to find some form in London ahead of the World Championships next month.

The 28-year-old told reporters: "I won't know how it is until tomorrow. I have worked hard in training so we will see how it is. This will be my test for Beijing.

"I'm very excited for Beijing and a little bit nervous. I set the bar quite high last time. I am not going there to lose - I always ensure I am ready for Championships. For me, it just takes one run to get to 9.7. It is the first 40m that is important and if I get that right, I know I'll be ok."

Bolt has won six Olympic and eight world gold medals during his illustrious career.