"The bombings in Baghdad - both on Parliament and the bridge - carry huge symbolic significance.

"The attack on Parliament was a clear attack on the democratic system which is, of course, enormously symbolically significant. But in practical terms, the incident also showed that the bombers can get straight into the heart of what was meant to be the most protected place in Baghdad. Therefore, in effect, it serves to send out the message that nobody is safe and that the insurgents can get suicide bombers in anywhere.

"The reality is that, despite its reputation as a heavily fortified and protected area, the Green Zone isn't actually that impenetrable. Within the zone itself live 15,000 Iraqis who go in and out every day. And although there are numerous checkpoints both outside and inside the Parliament building, it has long been feared that al-Qaeda has the ability to infiltrate the Iraqi security guards working there to smuggle explosives in. It is possible that this was the case in today's bombing of the Iraqi Parliament.

"Several security breaches in the Green Zone have recently been reported by the Americans. Last month, Iraq's deputy prime minister, Salam Zikam Ali al-Zubaie, was injured in a suicide bombing inside the zone, which killed several people. Recently, the Americans also reported that they had found two suicide belts within the zone. In that particular case, it is likely that somebody realised that they could not get past a certain checkpoint and dumped their explosives before they got there.

"Meanwhile, the attack on the al-Sarafiya bridge is also believed to be extremely symbolic. The east of Baghdad is mainly Shia while the west is mainly Sunni, and the Parliamentary speaker today said that the insurgents are conspiring to divide Baghdad in two. This particular bombing - destroying one of the main access points uniting the city - illustrates this well. Significantly, the bridge also has extra symbolism as it was built by the British in the colonial period so it is seen as an attack on UK interests as well.

"There are, of course, other ways to get across the city apart from this particular bridge. But the fewer there are, the greater the chance of those who use them getting caught up in bombings. The chances of Shia and Sunni residents having to move into each other's areas to get around also increases, which raises the possibility of further sectarian strife as they do so.

"Inevitably, as a result of today's escalation, there will be more checkpoints. But, although superficially guaranteeing extra security, such moves actually place some of the population in greater danger, as cars generally have to wait an average of five minutes at each checkpoint in order to get past - which makes them sitting ducks for the bombers."

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