From holiday gateways to heavily guarded rings of steel

They were once viewed as the glamorous gateways to foreign lands.

They were once viewed as the glamorous gateways to foreign lands.

In the 21st century, however, airports are more likely to be heavily guarded rings of steel - and not just in major world centres such as London and New York.

Forget about dropping your relatives and friends off outside the terminal at Glasgow Airport. In most modern airports armed police are almost as common as air stewards.

Railway stations have also stepped up security following the devastating attacks seen in Madrid and Mumbai.

Security expert Professor Chris Johnson, from Glasgow University, believes transport infrastructure will continue to be a target for terrorists.

He said: "These people are looking for high-profile places where there are lots of people, where they won't look conspicuous with say, a suitcase, and are unlikely to be closely observed."

There is little doubt that in the post-9/11 world, security can be a difficult balancing act for governments and those who run transport hubs.

Visible, effective measures are required to protect passengers and staff, and deter potential terrorists. But make the whole process of travelling too time consuming and inconvenient, and you risk losing passengers and money.

The response from Glasgow Airport's owners, BAA, after the bomb attack appeared textbook. Just 24 hours after being a terrorist target for the first time, with the eyes of the world upon it, it was open for business again. However, only good fortune had prevented a bloodbath on June 30 and BAA surprised no-one when they said security would have to be increased even further.

In the immediate aftermath of the attack, the road in front of the terminal was completely closed to traffic, temporary concrete and steel blocks were placed along the concourse and armed police patrols were stepped up. Four months later, BAA Glasgow announced a raft of measures, costing £2m.

More than 300 bollards, placed one metre apart, are still being installed in front of the terminal, to prevent vehicles being driven into the building.

It is believed Kafeel Ahmed skipped through a barrier behind a taxi. A spokeswoman insisted extra barriers and foot patrols by guards had since been introduced and would help prevent a similar incident.

According to Professor Johnson, however, another UK attack is inevitable.

He said: "There are literally dozens of different ways to attack transport infrastructure, and as explosive technology moves on, we have found ourselves in an arms race."

However, he was keen to put the risk into perspective, saying: "No attack is likely to be as devastating to the population as, for example, a flu epidemic, or a major flood, and the government recognises this."