European Union countries facing a growing influx of migrants should learn lessons from Bulgarian efforts to beef up external frontier controls, David Cameron said as he visited the border with Turkey.
The Prime Minister was shown a section of a new razor-wire security fence erected to deter would-be illegal crossings - many by refugees from the civil war in Syria and other conflicts.
Some 27,000 have come in via the 150-mile border between the two countries this year - part of a spiralling crisis that has left the worst-hit countries struggling to cope and left the border-free Schengen agreement close to collapse.
EU states have agreed emergency action to try to shore up the 28-nation bloc's external borders with stricter controls - as well as an aid package for Africa and Turkey to try to prevent so many migrants seeking to cross into Europe .
The revelation that some of the Paris attackers arrived via Greece - whose islands have borne the brunt of the sharp increase - has only increased pressure to impose more effective checks.
Britain has already committed border officials to provide the equivalent of 60 months' work helping screen individuals arriving in Greece and Italy and is considering whether to expend that support.
That is not likely to cover Bulgaria, which has already installed 21 miles of new fencing - and plans another 62 miles - and has deployed up to 1,000 extra troops to the border.
Mr Cameron travelled to the Lesovo border crossing and the nearby Elhovo control centre with Bulgarian counterpart Boyko Borissov - after holding talks in Sofia last night to bolster support for his EU reform proposals.
After chatting with border patrol officials, he urged others to learn from the Bulgarian approach.
"Britain has always maintained - and will always maintain - our own borders," he said.
"We are not in the border-free Schengen Zone.
"But it is important that Europe has strong external borders and here in Bulgaria you can see a prime minister and a government that is absolutely committed to that.
"They have got a sea border that they protect, they have got a land border with Turkey that they protect and I think there are real lessons to be learned here about (how) if you give it the priority you can get it done.
"So we should continue to support them with the important work they do."
The Bulgarian authorities have faced strong criticism, however, from Oxfam over the alleged abuse of migrants - and one young Afghan man died, apparently the victim of a ricochet from a warning shot fired by the authorities.
Sofia hopes the burden may be eased in part by an EU financial package to help Turkey absorb more of the migrants flowing over its border with Syria - towards which the UK has offered £275 million over the next two years.
Mr Borissov joked that he wanted to give Mr Cameron "a geography lesson" to end his two-day visit.
Many European leaders had "forgotten that our border with Turkey and our sea border is longer than the border with Greece", he told reporters.