The form for free health care in Europe counts for little in a spot of bother,
Fifty thousand Britons fall ill on holiday every year. This summer, our daughter was one of them. We had travel insurance, we had our E-one- eleven certificate - so why did we end up paying for treatment in a European country?

In ancient days, the prudent traveller set off with the protection of a St Christopher talisman. The modern mantra "don't forget your toothbrush" does not have the same protective qualities, yet it seems this is all many of us rely on. A staggering 6 million trips abroad (about 20 per cent) are taken without travel insurance. Many people have never heard of the E111.

E111 is Post Office jargon for a slip of paper giving "Entitlement to Benefits in Kind During a Stay in a Member State". Briefly, this means that free or reduced-cost emergency medical treatment should be available when you travel in the new European Economic Area (EEA) - EU states, plus Austria, Finland, Iceland, Norway and Sweden.

I had my E111. I had travel insurance, Green Card, bail bond and even my toothbrush. This should have been enough preparation for a week in the Costa Brava, but I had not reckoned on the vagaries of applying documents to real life.

Our holiday was uneventful, medically speaking, until the last day. As we were about to leave the camp-site, seven-year-old Frances started screaming and scratching her chest, which was red and raw. I recognised the symptoms of prickly heat, an intense form of sun-induced itching.

Cool baths help, but symptoms can take days to clear. Standard medical treatments involve antihistamine tablets. We applied a cold flannel, but as we set off to catch thetrain, our patient got worse.

Luckily, there was a surgery outside the camp-site, and it was open. I marched in with my wailing daughter, waving my E111 form. The receptionist asked a few questions ("name?" "fever?") and we lifted Frances's T-shirt to show the blotchy marks.

Would it be free? "Oh no," said the receptionist. The cost of an appointment would be 6,000-8,000 pesetas (pounds 31 to pounds 41.) Medicines would be extra.

I showed her my E111, but she wasn't impressed. All Spanish doctors were private these days, she asserted, adding with audible disdain that there was some social security, but we would have to travel miles to find out about it. It was nearly midday and we had a train to catch. We turned to leave, but the receptionist ran after us - apparently the doctor would see us now. I presumed he had been overwhelmed by humanitarian feelings.

In his darkened surgery, the doctor (a German) took Frances to an electronic dentist-style examination chair. He looked in her eyes, tapped her back and listened while she said "aaah". Then he asked me if she had had measles. "Measles?" I repeated disbelievingly. "No, but..."

He tried a different tack - what about Windpocken? Wind is the German for wind and pocken means spots, so I agreed and started to explain about the prickly heat. But the doctor, engrossed in his medical translation manual, emerged triumphantly with "chickenpox!" I assured him Frances had already had it, but neither this information nor the fact that her current malaise in no way resembled chickenpox could deter him. "Sometimes they come back," he said.

He prescribed medicine to quell Frances's non-existent fever and a soothing gel, telling me to watch out for spots appearing in her mouth. After this charade, we were ushered back to the receptionist, who presented me with a bill for 5,000 pesetas. A quick whip-round revealed we possessed even less cash than I had thought. In the end, our hosts accepted a British cheque made out for 6,000 pesetas.

We chased through town to find a pharmacy before its habitual four-hour siesta and raced north, catching the train with 10 minutes to spare. Frances's condition improved with the prescribed gel, but fever, measles and chickenpox never did appear.

Misdiagnosis can happen anywhere, but it is galling to have to pay for it - and this was emergency care for a child. Back home, I read the small print in the E111 handbook, called Health Advice for Travellers. For Spain: "Treatment under the EEA arrangement is only provided by practitioners within the Spanish health care system, and in some parts of the country you may have to travel some distance to attend a surgery, health centre or hospital within the health scheme."

Even with an E111, you have to pay up to 40 per cent of the cost of Spanish medicines (unless you are a pensioner) and dental treatment is not covered at all.

Each country has its own idiosyncratic way of applying the rules, and in an emergency, it is easy for the traveller to get tripped up by red tape. In Austria, you must apply to the Regional Health Insurance Office before seeking a doctor; in some countries, you pay and claim a refund. In others, treatment itself is free. In many places, you might do better to go direct to a pharmacy if you know what medicine you want.

Finally, I presumed my travel insurance would provide where the E111 had failed. But here the small print reminded me I was liable for the first pounds 35 of any health claim - almost exactly the sum I had spent to be told my overheated child had measles.

There was only one consolation to this sorry tale. When I asked my bank about the validity of an ordinary cheque written out in pesetas, they were sympathetic. "Don't worry," they said. "The Spanish banking system is so slow it might never get through."

l You can obtain an E111 over the post office counter - just take along your National Insurance or NHS number.

l Once obtained, the E111 remains valid indefinitely unless you move outside the UK, or use it to claim for treatment.

l Keep a photocopy of your E111 with the original - the copy must be handed in to doctors in Belgium, France, Germany, Italy, the Netherlands and Spain.

l The E111 covers the holder and any dependent children under 17 (or under 20 in full-time education).