Sometimes in life you come across people who I refer to as 'lone nuts'.

A lone nut is someone who puts their head above the parapet of life, and swims against a strong tide.

Why do they do it? they believe in something. They believe it's time for change. They believe passionately about being a force for good.

It's not an easy path.

Once you lift your head above that parapet, it won't be long before you get shot down.

The criticism, the scorn will follow. Who do you think you are? You're an attention-seeker. Perhaps you have an agenda? Why are you swimming against the tide. It was flowing perfectly well until you came along.

And at times, in the the midst of all of this, 'lone nuts' will doubt themselves and wonder whether it's worth it. But they know it is. so they fight on.

They don't know it at the time, but they'll later realise that the path to great change is almost always preceded by a period of chaos.

In a moment, I'm going to interview a 'lone nut'.

Her name is Kathrine Switzer.

50 years ago, she ran the race of her life.

She was just 20 at the time, and running in a men-only race.

That race was the Boston Marathon.

What happened on the course that day, just after the two mile mark, was unimaginable.

But fortuitously it was captured by a photographer.

And that photo of Switzer would later go on to be included in time magazine's "100 photos that changed the world."

She is a true 'lone nut'

LISTEN TO RACHEL'S INTERVIEW WITH KATHERINE SWITZER HERE