Not even in Congo or Bosnia at the height of conflict had I ever had to sit down to write a story without a cup of tea, a glass of water, a bar of chocolate or a dried fig.

It was not much fun. I had heartburn, headache, sore throat, furry mouth and I just want to lie down and go to sleep. Not eating is easy. It is not drinking, especially not drinking tea, that hurts most.

This was all the fault of Boris Johnson, the Mayor of London, who has urged non-Muslims to fast for a day during Ramadan to help them empathise better with their Muslim neighbours.

Discreet enquiries established that Boris himself was not intending to follow his own advice. He had given up alcohol during his electoral campaign and thought that was sufficient.

So I called a senior member of Britain’s 1.6 million-strong Muslim community for advice. He was with Boris. “Are you fasting?” He laughed. “In Islam, you only have to believe two things: There is one God and Mohammed is his prophet. Everything else is optional.”

Try telling that to the 155 people detained this week by police forces in Aswan, southern Egypt, for publicly eating, drinking or smoking during daylight hours.

Fasting for a day certainly achieves its objective of invoking compassion for those who go hungry and thirsty every day.

Imam Shahid Hussain of the Central Mosque in London recited the Salatul maghrib, or the post sunset prayer, at the iftar, or fast-breaking evening meal, hosted by the new US ambassador to London in Regent’s Park on Thursday night.

He said Islam, by asking believers to fast for 30 days during the ninth month of the lunar calendar, was following in a tradition set by Judaism and Christianity.

I learned the discipline in a strict but loving Christian household as a child, where all sweet food during the 40 days of Lent was foregone and all food of any kind until a spartan evening meal of fish and broccoli on Fridays. But at least we could drink water.

Dr Naseem Tariq, a surgeon whose wife Rubbena Aurangzeb-Tariq, an artist and art therapist, took me to Central Mosque for Friday prayers, explained: “The underlying Ramadan theme is to teach patience, appreciation, control, sacrifice, endurance, unity and perseverance. I find it quite stress-relieving too. Basically no food, water, drink of any sort, no smoking, no alcohol, no drugs, no sex, no gossip, all forbidden until Iftari, whereas being kind to others is desirable.”

The gossip bit was going to be the hardest part, I thought, but I had not reckoned on exhaustion. By midday even talking was an effort, never mind exchanging information about another person. Jamie Oliver believes healthy eating will reduce the discipline problems caused by over-active children in schools. In my view, speaking from the experience of just one day, the answer is giving them nothing to eat at all.

I had been instructed by Rubbena, whose seven-year-old son insists the family fasts roperly during Ramadan because he enjoys he iftar spreads so much: “No food or drink after 5.30am.”

So it was up at 5am for a nice soul-warming breakfast of juicy sausage and eggs but I remembered just in time - forget the sausage. In the end it was aptly shaped croissants with blue berries and strawberries and gallons of tea and cranberry juice. As I was eating, I read some of the Prophet’s Ramadan sermon online and bits of the Koran but really just wanted to get back to bed.

Hiccups and indigestion kept me awake and woke the rest of the house.

So I resorted to the ultimate modern fasting tool: Ramadan on Twitter. There were some staggeringly beautiful rosy dawn-and-dusk Ramadan photographs. There was a baptised Christian turned Buddhist fasting for Ramadan in Kashmir, a non-Muslim fasting for Ramadan on YouTube, and a poll asking readers which of the privations he would find it hardest to overcome. (I ticked the not-drinking box).

It was all worth it, though, when I broke fast at last with Rubbena and Dr Tariq. Even when you’re not fasting, properly cooked Asian food is good. When you are truly hungry, it’s like a taste of paradise.

Ramadan ends at the end of this week, amounting to 30 days in all. One day was hard for me and it took a weekend to recover. I’ve emerged with a new respect for Muslims around the world - just as Boris wanted.