The Chupa Chups lollipops, whose wrapper was designed by Salvador Dalí, were supposedly presents from South American in-laws. But one lick would give any child a Surrealist experience — they were filled with cocaine.

Likewise, no baby was allowed to wear the rather precious nappies discovered in a suitcase at Barajas airport, Madrid. The reason: they were impregnated with the same drug.

The junior occupants of two prams that arrived at the airport were sitting pretty until the Customs officers spoiled the party by discovering cocaine hidden under the seats.

Babies, it seems, are the latest cocaine mules. For Luis Alonso and his Customs team at Barajas airport, on the front line of Spain’s war against drugs, every day is a struggle to keep pace with the traffickers’ ruses.

“We think we have seen everything, then they try something new,” Mr Alonso said. “They made a plaster cast made of powdered cocaine and the man’s leg was really broken. They try the same things with cargo. I have seen knitting bobbins, paintings, fruit — you name it — filled with cocaine.

“The latest thing are chunks of cocaine made to look like beans. We didn’t detect them until we squashed one and carried out a drugs test.”

In the battle of wits between law enforcement agencies and the cocaine cartels, the traffickers have been forced to come up with ever-more inventive ways to get the drug into lucrative European markets, including Britain, their biggest customer.

A dog recently appeared agitated even though it had not spent very long in the hold. An examination by Spanish Customs officers found that it had undergone surgery to hide cocaine cylinders planted in its stomach.

Another passenger appeared to have returned from holiday in Scotland carrying two bottles of Scotch. Closer inspection revealed that they were full of white powder, not malt.

Thousands of passengers arrive at Barajas airport every day on about 650 flights. Some take the 45 “hot-flights” from cocaine-shipping destinations such as Bogotá, Caracas, Buenos Aires and Santo Domingo. As Spain’s biggest airport, Barajas attracts the highest number of traffickers and cargo shipments. Mr Alonso, his team and Guardia Civil colleagues, attempt to stop cocaine reaching the streets of Spain, where it sells for £52 a gramme. Eighty per cent of the cocaine that slips through the net is shipped on to Britain and other countries.

Mules are paid between £3,500 and £7,000 by the gangs. Most wrap the drug in a condom, then swallow it; if it splits the pure cocaine kills in minutes. “They don’t care. Some seem tranquil when we arrest them. Others are nervous. Some are 80-year-olds, others kids,” Mr Alonso said.

Times Recommends

• Oprah Winfrey says goodbye to her talk show
• Focus on the big issues, not the bananas
• Václav Havel — symbol of national liberation