An unforgettable realisation hits as I travel.

We wake up early on a September morning to head to the train station. Crashing at a friend's house, we're able to travel without our backpacks. We are out to experience this city we know so well from books and history; any weight will only slow us.

So excited are we on the train that we can barely sit . We point and exclaim at all the place signs. Neither of us has been in a train this long before. Where we're from, the trip would more easily be done by road. Our fellow passengers throw us knowing glances.

I take out my guidebook. We are half an hour from the city and have an all-day pass for its trains and buses. I look across the aisle to my travel partner and I know he wants to see all the biggest and brightest sights. We really should have spoken last night. I am sure we can strike a compromise.

We get off at a station milling with workers; ties flying, heels clapping, coffee and laptops hastily put away. Then there we are; two young people in jeans with small backpacks and bright eyes. We walk out into the sunny day with expectant strides.

This city dwarfs ours in so many ways; hardly what one would call getting off the beaten path. We point at things and take in the city’s sights with awe . There it is-our favourite detective's house. Look, if we focus we can conjure this or that famous event in history. We head off to one of the city's most evocative spots and line up at the entrance.

When we get to the security check, the guard asks to look inside our bags. I'm fine with this; my country has been hit by more than one terrorist in its time. He asks the usual questions-where we are from, how we are liking the city-as he looks into my partner’s bag. Mine is next.

The question that follows I will never forget, "Are you carrying any knives?" Am I carrying any knives? I turn to my travel partner, my bewildered 8 year old brother. Would I carry a knife, ever? I look back at the guard. My eyes ask ‘Why?’ and he launches into a tale about all the girl gangs in the city, the knife crime. The things he doesn't say I can hear like a siren; the things too incorrect to say yet hovering like a cloud above us.

"No," I say, "No knives." Something goes off inside me and I stride with more purpose into the Tower of London's grounds. Tramp those grounds, I tell myself. Enjoy every moment; there are no knives here to cut it short.