The attached document looks at the current terrorist threat from around the world including the UK. Parts of the contents are as follows:
The Prime Minister and security chiefs have reviewed the risk of a Paris-style attack in the UK. They (have) agreed that elements of the Paris attacks should be considered when planning future training exercises for the police and security services. The Director General of the Royal United Services Institute also said that Islamist extremists were now intent on launching "marauding attacks", rather than targeting aircraft adding that the extremists were switching tactics.
The on-site management and security team are briefed and aware of the ever-changing situation and change the procedures on-site accordingly. This means that occupiers might occasionally see changes in the security set-up or processes that are carried out on site.
The link below contains more information