What inspired The Shard’s design?
It was very important to us at Renzo Piano Building Workshop that such a tall building was accessible to the public. Around the world, the tall buildings that are known and loved are the ones that people can access, such as the Eiffel Tower and Empire State Building.

It had to be functioning seven days a week, which led to the mix of uses – offices, restaurant, hotel, some apartments and a viewing gallery. The gallery is aiming for one million visitors a year and there are only 10 residents in the apartments, so they have very different uses, but are in the same building.

We wanted to create an open building so avoided using heavily tinted glass, which blocks out all life going on inside. You can see lights on inside, which show it’s functioning. By inclining the sides, the glass reflects the sky and the weather, so the building changes throughout the day. The spire doesn’t meet at the top, so visitors feel the London air.

How does The Shard enhance the capital city’s skyline?
London isn’t New York, Singapore or Hong Kong, where a tall building is just another skyscraper in the forest. In London there is no forest; the building is set against the sky. The Shard’s spire shape is a form that has resonance throughout the UK as it echoes the outline of its historical churches.

It also represents the masts of boats that used to moor in the Thames – tall, slender elements that rested against the skyline in old London.

What is the design’s message?
The building might be privately financed, but it’s not just a commercial venture – it’s a building that the public can enter: to visit the restaurant; stay at the hotel or experience the view.

What was the brief?
The most important thing with a good building is a good client. The client listened to us and we listened to them. It was a shared vision.

Initially they didn’t like the sound of a viewing gallery, but then realised it had commercial viability to it as well as a socio-political importance in gaining acceptance of the project.

What were the challenges?
The first challenge was planning. This building represents a change for the city. Not only is it substantially taller than the others, it’s mixed use, which no other tall building in London is. It took three-and-a-half years to get planning. The principle opponent was English Heritage. There are protected views of St Paul’s Cathedral and we’re in the backdrop of two of those views. We argued that as we’re replacing some pretty uninspiring views, we’re improving the situation and fortunately the planning inspector agreed with us.

Getting tenants was another challenge. Fortunately the client got two tenants early on – Shangri-La took the hotel in 2005 and Transport for London took office space in 2006.

The biggest challenge was financing the building. The client had financing in place in 2008, then the credit crunch came and the funding was withdrawn. Fortunately the Qatari government had also been interested and they stepped in as both investors and financiers.

What’s the evacuation process?
We use the lifts to get people out – they have a back up power generation and smoke pressure relief and are quick and safe.

How does the architecture enhance the experience?
You could argue that you could see the view from the top of a beanpole, but the building is important. Consider the Rockefeller Center and the Empire State Building. In many ways the Rockefeller’s view is better, but the latter gets many more visitors because it’s an iconic building.

I hope people come to visit The Shard because they’re interested in the building, as well as the view.

William Matthews is project architect at Renzo Piano Building Workshop Attractions Management, Q1 2013