If you were prime minister for a day, what issue would you cover first and why?

Guaranteed annual income for everyone. The world is too advanced to have people staving or malnourished.

Close down our detention centres on Nauru and in Papua New Guinea and set up an asylum seeker processing centre in Indonesia.

End the fucking drone strikes in foreign countries. Do we get so arrogant we think we can handle other’s problems better than they can?

Address climate change meaningful.

Get a hold on the radical Muslin infiltration of my country.

Edit: meaningfully. (Need coffee!)

Make some changes to the education system.

I’d fuck Cameron’s wife & find time for tea & scones between sessions.
She’s not too attractive, but it would piss Dave off big time.

Here in the US being Prime Minister would probably get me a cup of coffee; if I had a dollar as well.

Food, shelter and medical care for everyone. Maybe it’s not realistic based on an economical standpoint, but ironically, as @talljasperman said it is entirely possible.