Wednesday 22 March

I arrived at London Waterloo yesterday afternoon intending to walk to the National Gallery in Trafalgar Square before returning to the South Bank to meet a friend and go to a concert in the Royal Festival Hall. It is a very pleasant stroll across the Jubilee footbridge looking down the river towards Westminster and I used to do it every day when I worked in London.

As my train approached the platform I could see that the entrance of St. Thomas's Hospital A&E was crowded with ambulances and police cars and that traffic was stationary on surrounding roads. The air was resonating with the sounds of sirens and helicopters and when I reached the South Bank I discovered that the whole site was taped off and that it would not be possible to walk across the river. Behind me a police van was shouting at pedestrians and telling them to clear the area.

These are the things that I saw and heard and my question to you is what would you do next if you were in my situation? Would you find another route across the river and continue with your plans for the evening or return to Waterloo, a crowded train station. How would you get information about the safest place to be?

I turned to Twitter and read on @BBCBreaking that the incident was in Westminster so my alternative route was out of the question. @MetPoliceUk were giving advice on roads that were closed and it was apparent that the incident was very serious with a large cordon around Westminster Bridge. There was no evidence of coordinated attacks in other parts of London but I checked @southbankcentre and saw that the site had been closed on police advice. @LPOrchestra quickly confirmed that the concert was cancelled and so I could make the decision to return home.

In contrast, my friend chooses not to have a smart phone or use social media and apps and I realised how vulnerable she has made herself by rejecting changes to the way that information is shared. She was dependent on other people before she could make decisions about the safest course of action and because reception for analogue phones is poor when everyone else is using their phones it was difficult for her to keep in contact.

I learned two things yesterday:

1. You do not know when you will be in a fast moving security situation. It could be a train station, a concert hall, an airport, a shopping centre. Think about how you would access information to keep yourself safe. In my experience Twitter is the quickest way to get information from reliable sources so it is worth investing time to become familiar with how it works.

2. Always have a fully charged back up battery for your phone in your bag. If areas are cordoned off or transport stops you may be using your phone for several hours and your family will need reassurance that you are safe.

I hope that you are never in a situation where this advice is helpful but please be prepared so that you can make informed decisions and stay in touch with your family.

This post is dedicated to those affected by the incident at Westminster on Wednesday 22 March and to the emergency services for their work protecting the people of London.