Billionaire philanthropist Bill Gates says he is crossing his fingers that a deadly flu epidemic does not strike in the next 10 years because the world is "a bit vulnerable right now".

Mr Gates, whose foundation invests in improving global healthcare, said the Ebola and Zika crises showed the systems for responding to emergencies are still not strong enough.

He was speaking to Dame Sally Davies, the Chief Medical Officer for England and BBC Radio 4's Today programme guest editor. She revealed that her department had recently rehearsed a "nasty flu" scenario. She said in the UK the NHS was "pretty well prepared" but it would take at least six months from the start of a flu pandemic to get an effective vaccine.