Just a Minute is a BBC Radio 4 show and it's so called because guests are asked to talked on a random subject for 60 seconds without "hesitation, repetition or deviation". It's harder than it sounds!
I've made a page here on nimisis that lets you practise this. You don't get penalised for hesitating, repeating or deviating, but it's an interesting exercise anyway.
You can try it out here.