The siren that cut through the night in Praia da Luz last Thursday was a new experience for most of the expats and holidaymakers frequenting the resort's bars, restaurants and terraces.

For some of the older residents it jolted memories of past fishing boat disasters, the original reason for the siren's existence.

This time it was a different sort of emergency but the effect was the same - people stopped what they were doing and followed the crowd to see what they could do to help.

When they found out why, it came as a shock to a community built over the past 20 years on the safe care of children on holiday.

Children are a regular sight around the village, lines of them hand in hand being led from one play activity to the next by staff from the Mark Warner Ocean Bay Club resort where up to 90 families stay.

Duncan Kemp, who runs the Carib bar and restaurant with his wife Angela, said: "People come here because they consider it to be a place that is extremely safe for children. That is why it is popular with families. The Portuguese love children, they dote on them.

"Mark Warner are a company with a reputation for looking after children, that is what they do. They have a whole team of child-minders and a reputation for being excellent at what they do. We get parents in here who have come for a drink and a meal or a game of tennis, knowing they have left their kids in safe hands."

Praia da Luz is part of a ribbon of development running along the Algarve. Portugal's southern Atlantic coast is popular with domestic holidaymakers and old colonials from Mozambique, Angola and Guineau as well as British expats who go to retire or run small businesses and the thousands of British families who holiday in the summer and - later in the year - golfers.

"Thanks to the golfers - who spend more per capita than regular tourists - we can extend the season instead of worrying about laying people off," said Mr Kemp, 73.

A Londoner of Scots descent whose parents, Jack and Jenny, were MPs in the post-war Labour government, he moved to the Algarve 19 years ago when Praia Da Luz was little more than a fishing village and a far cry from the hectic pace of south London where the couple worked in the licensed trade.

"We all hope there will be a happy outcome to this," he added. "There has been a lot of support - there has been a huge effort by the authorities and the locals. The siren went off at 10 o'clock on Thursday night and people were out looking until 4am.

"They had helicopters out today but there is a lot of ground to cover. There is a very thin band of development along the coast where we all live on top of one another because it is by the sea, then you get open country behind it. There are large fields, a lot of farmland behind it, which will take a lot of manpower to search thoroughly.

"Abductions of children are very rare in Portugal.

"We have never seen so many police here."