It was over 30 years ago that Norman Foster in one of the earliest commissions for his self-titled design firm penned the now famous headquarters for Willis Faber and Dumas in Ipswich.
The open plan offices, glass curtain walls and organic shape all proved revolutionary and in 1991 it became the youngest building to ever be given protection by English Heritage when it was listed.
Since then Willis Faber & Dumas has mutated into its current form, the Willis Group, and when they wanted a new headquarters the architectural wheel had turned full circle. They were struck by the plans Norman Foster had drawn up for British Land to replace a hulking groundscraper on Lime Street opposite Lloyds of London.
Having employing the architect to tweak the design more precisely to their specifications, construction work began in 2005 with the final employees of Willis moving into their new global headquarters almost three years later in April 2008 finally merging the operations of four offices into one.
Externally the 124.9 metre tall building is notable for its stepped appearance with its glass concave front and seemingly serrated edges on the back portion of the building that are angled to minimise solar gain. Further improvements are made from the glass that turns a reddish hue from the outside when observed reflecting the direct sunlight.
Outside the Willis Building, the streetscape has been remodeled with new paving and public areas expanded thanks to the recessed ground floor that allows pedestrians to walk directly under the building.
Sharing a new public space to the east next door is another shorter curving building also built as part of the same development, the Fenchurch Avenue Building, that the Willis Group has leased and then sublet to other companies.
Entering the building through the glass front immediately leads to an impressive area that emphasises space without appearing too stark or unobtrusive. Although clutter is kept to a minimum, the curvaceous walls and glass allow the light coming in from three aspects to texture the entire area in lieu of more obvious décor.
A nod to the neighbouring Lloyds of London is made in the form of the staff uniforms that greet you - retro red is the order of the day just like the doormen opposite. Sadly however, there isn't a top hat in sight.
Sweeping round behind the lightness of the entrance area is the contrasting lift lobbies. Clad in black marble flooring, metallic textures and blue lighting, a sci-fi aesthetic is the order of the day.
Smoothly sweeping you up to the top floor in a mere 15 seconds if you travel without a stop, is one of 21 lifts that reach a top speed of 15 miles per hour.
Reaching the 23rd floor reveals an exclusive roof terrace that occupies all of the middle step of the building and gives impressive views looking directly over Lloyds of London and towards the Gherkin.
Adjacent to the terrace at the back of the building is the exclusive 40 seat Client Advocate Restaurant with its curving glass curtain walls that allow panoramic views of Canary Wharf and much of the eastern half of London as the rich and powerful dine in luxury.
For ordinary staff there is the 16th floor that also has a similarly sized outside space, this time taking up the roof of the lowest step. It's a place for the Associates to come and relax after they have had a bite to eat in the 300 seat restaurant, One Flag Café.
The real point of the building isn't the dining opportunities or spectacular views but to work as a well-greased machine that keeps the cogs of the Willis Group running.
Drawing on the example set by the Willis Faber and Dumas building in Ispwich, open architecture is employed throughout the office floors going as far as possible to eliminate boundaries in an attempt to not only create an open environment, but also to flood the building with natural light and provide outside views no matter where someone is working above ground.
If you want to see the building for yourself, it will be open as part of London's Open House this summer, although, as ever, we recommend you get in early and book because tickets for this will fly off the shelves.