By James Cook BBC Scotland news presenter

The illness began before dawn on Thursday morning. It was still dark as I was awoken by stomach cramps. I rolled over and tried to go back to sleep. The pain got worse. I pulled the covers over my head.

It got worse still and I hauled myself out of bed and into the bathroom. I drank a couple of glasses of tap water and went back to bed.

For the next few hours I tossed and turned, trying and failing to ignore the pain in my stomach and get back to sleep.

At 0900 BST I got up again, the pain was still there and now it had been joined by diarrhoea. I drank at least two pints of tap water and went to work.

The parasite can cause vomiting and diarrhoea

As the day went on the diarrhoea got worse, the stomach cramps remained and I began to feel a 'flu-like ache in my arms and legs.

I couldn't eat and I couldn't figure out why I felt so ill. A meal I had eaten the night before had tasted fine, I hadn't been drinking alcohol and I'm usually pretty healthy.

My colleagues reckoned I had a nasty 24 hour bug which had been going round. I would feel fine in the morning, they said.

But Friday came and I felt worse. I went to work anyway and by the time I was presenting Newsdrive on Radio Scotland at 1600 BST I was wishing I had stayed in bed.

'Drink plenty of water'

I had to run to the loo during the programme and I sat in the studio with my head in my hands. The stomach cramps came in waves. My limbs felt as if they were twice their normal weight.

"Go to your bed early and drink plenty of water," everyone advised. I did, from the tap. Pints and pints of it throughout Friday evening.

Something about the taste made me say to my girlfriend: "I'm beginning to think it's the water that's making me ill." She replied: "There's probably some sort of bug in it after all that rain."

James felt better after changing to bottled water

Not only was she right - but Scottish Water already knew that she was right. Its officials had seen the results of tests which confirmed that Mugdock Reservoir in Milngavie, which is pumped to my flat, contained high levels of the parasite, cryptosporidium.

It would be another 24 hours to inform the public. Another 24 hours of diarrhoea, stomach cramps and aching limbs for me - and another 24 hours before I stopped drinking the contaminated water.

So, unsurprisingly, my illness continued throughout Sunday and in the evening I watched in disbelief as Dr Jim McMenamin of Greater Glasgow Health Board told the BBC's Reporting Scotland that no-one was ill as a result of the scare.

Tests on Thursday

I called the helpline number at the end of the report and was told that my illness had nothing to with the water. "I have all the symptoms" I protested. "But it takes two to 10 days for the symptoms to show" was the reply "and the bug wasn't detected until last night."

This was not true. As we now know, tests had been carried out three days earlier, on Thursday, and the parasite had been confirmed in the supply on Friday.

I asked when the water was likely to be safe to drink again, "We don't know," the woman on the helpdesk replied, "In the meantime you should boil any tap water before drinking or using it to prepare food, brush teeth or bathe babies."

"Will Scottish Water be providing bottled water?" I asked her. "No," she replied, "your water is drinkable if you boil it, so as far as we are concerned, you still have a water supply."

All water should be boiled before use

Unconvinced that the water was not to blame for my illness I asked for health advice and was advised to call the NHS helpline.

The operator agreed with me that I was showing the exact symptoms of the cryptosporidium bug and said I should contact my GP.

Now, on Monday, as more people report the same symptoms, Scottish Water continues to insist that no one has fallen ill as a result of the scare.

I have stopped drinking tap water and have switched to bottled. I am feeling better already.