leaders from around the world gather to pay their respects. i m outside where the event will be taking place this afternoon but there was growing opposition from protesters citing the legitimacy and the cost. and work begins to remove the tens of thousands of floral tributes left to honour the queen in central london. welcome to the programme. it sounds like a hollywood film, but in under 15 minutes time, the american space agency, nasa, is going to crash a rocket into an asteroid. it is the agency s first planetary defence mission and scientists there are about to try diverting the path of an asteroid by crashing a spacecraft the size of a small car into it. it s a test to see if something similar could be done if an asteroid was heading towards earth in the future. our science editor rebecca morelle has the details. it s a cataclysmic scenario. an asteroid headed for our planet, with the potential for mass devastation. it s happened before. a space rock wiped out the din