I'm into the last 3 hours doing Live Below the Line - and I've encountered a problem.
After 15 hours in transit from London - where I drank the tap water I brought with me, ate the 2 bananas I took with me, and eschewed the food on the plane, I'm in Bangkok.
I've just checked into the very nice hotel, and went to fill up my bottle, only to discover that tap water in Bangkok is not potable.
I can't 'afford' bottled water.
I've only got 3 hours to go, but this is going to be a thirsty end - and a reminder of how hard life would be if my £1 a day was for everything - not just food and (free) tap water.
Being in transit, and now not being able to drink anything, have really hit home how hard extreme poverty must be for people.
The rest of the week, I could bend my time and behaviour around my Live Below the Line diet. I could go to the pub and drink water. I could avoid going to functions, I could cook all of my meals at home, and heat lunch up at work in the microwave.
But, once I went back to doing what I needed to do for work - in my case travelling - it becomes very different. I desperately wanted a beer on the plane, I wanted to eat the food on offer, I want to drink the bottle of mineral water on the desk in front of me. I won't, because I'm doing the challenge.
For the world's poor, it's not even a choice. They can't, because they can't afford it. And that's outrageous.
In a world of plenty, there's no reason that everyone shouldn't be able to eat enough or drink clean water.
That's why I'm so passionate about fighting poverty, and it's why I'm so passionate about our work at the Global Poverty Project to educate, inspire and activate citizens in the rich world to change our behaviour, and to change the rules and systems that keep people poor.