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The first Society walk of the year looked at some of the recent and not so recent engineering feats with the Square Mile. Jo East reports:

Our leader for today’s walk was Blue Badge Guide Caroline Dale. We started at the West Entrance of St Paul’s where Caroline explained the shape of the walk and asked us to consider the Cathedral not just as a piece of architecture but as a feat of engineering too. With this in mind and Setting a suitably brisk pace for a damp and cold Saturday Morning we made our way to One New Change (Jean Nouvel 2010). A clever piece of engineering in itself this mixed development of Offices and high end bars and shops affords from its roof terrace a view of St Paul’s (Christopher Wren 1675) that best demonstrates its engineering genius. The dome that we see from inside is in fact an inner shell with the outer dome merely a lead covered timber structure. This design in itself would however not have supported the crowning stone lantern, gold cross & outside public gallery so an inner brick cone was constructed to support this. This “outer wrap” idea carries on at ground level where Wren built a double set of walls running down the North and South sides of the nave. In this hidden space between the double walls outside Wren placed a line of buttresses to avoid cluttering the inside of the church with roof supporting columns.  

Our walk then took us to Bloomberg Place (Foster & Partners 2017) This elegant winner of the 2018 Stirling Prize’s most visible engineering elements are the brass fins that adorn the windows. Carefully modelled to give maximum solar gain to the building they contribute to making this vast site environmentally win awards for sustainability by vastly reducing the need for air conditioning. A more hidden feat was the restoration of the temple of Mithras to its original site after being wholesale transported by the City’s Fathers to a more convenient place in less enlightened times.

Passing under the building we arrived at Cannon Street Station. The original 1860s station has undergone various overlays and the latest is a large office development completed in 2007 (Foggo & Arup) Replacing a 1950s Poulson building the transformation was completed with no shut down of the station underneath and care for the important archaeological site on which the whole site is built The 16th Century Steelyard – The English outpost of the Hanseatic League. This was achieved by cantilevering the whole building across four supports (two each side – East & West facades) which are sunk well away from the ancient remains beneath. Seeing it from this perspective it gave me renewed admiration for this project which was opened with little fanfare as the City went about its business.

Stopping next at Bracken House (Albert Richardson 1958) Caroline pointed out the 1990s Michael Hopkins infill that demolished and converted the old metal foundry and printing press area that previously churned out the Financial Times. Turned into offices, the latest intervention being some unifying refurbishment by John Robertson Arch.s (2017) making it fit for the return of the FT to its old home. The robust use of bronzed steel and glass on the new parts giving a suitable echo of the heavy printing presses that once used to roll inside. Both the Hopkins and JRA works maintained the building’s Grade II listed status.

Pausing underneath the Millennium Bridge (Foster and Arup 2000) Caroline talked about the disconnect between Architect and Engineer that caused the famous wobble on opening. A lesson about the difference between the wanted and the possible.

A happier story was found as we walked along the embankment to Blackfriars Station (Pascall+Watson architects, with execution by Jacobs and Tony Gee and Partners 2012) where a photovoltaic array forms the complete platform roof of the Station. Overhauled to provide greater capacity for the Thameslink project this river spanning Station fittingly unites North and South banks where at one time in the past previous versions of Blackfriars station could be found. Thameslink itself is another invisible engineering feat. Burrowing under the City of London to realign previously above ground tracks to provide connection through the capital by joining up with existing ones at Farringdon.

An older “invisible” engineering marvel was the very ground where we walked. Joseph Bazalguette’s Embankment. After the Great Stink, where the Thames was so foul that Parliament was affected, he built North and South embankments of the Thames to contain (among other essential services) the vast sewer pipes intended to link up with London's old below ground drainage system diverting all effluent from reaching the Thames at all. Realising that to build a sewer system north and south of the river below the streets would have been too expensive, disruptive and time consuming, Bazalgette’s plan to embank the river not only solved this problem but also provided 52 extra acres in Central London. Today the Tideway Tunnel project – What Mayor Johnson called The Cloaca Maxima - is being constructed to deal with the now inadequate size of the original Bazalgette sewer pipes and consequent sewage overflow reaching the River Thames.

We then made our way following the route of the hidden Thameslink to a very visible piece of Engineering – Holborn Viaduct. (Haywood (arch) & Ordish (Eng) 1869) This first “flyover” was built to improve access between West and East. The previous road route between Holborn and Newgate went down a steep valley one side and up a steep valley the other with a single bridge - The Holborn Bridge - in between. The massive congestion on this awkward up and down route by the 19th Century made a new viaduct essential. Handsomely wrought in cast iron for me the inspiration was the 4 step houses on each corner providing covered walkways and suitably imposing buildings to the street below. We finished our walk at Smithfield Market – A hotchpotch of buildings that has plans for some of it to be redeveloped and some of it to become the new home of the Museum of London. As a finish to the walk Caroline told that when it came to look at the potential space the museum could occupy 800 square metres of extra room was discovered in long disused freight tunnels hidden beneath our feet. A timely reminder that much of the engineered City is hidden but none less impressive for that. With the two hours having flown by everyone thanked Caroline for being such an engaging host and hoped that she might lead more for the Society. To engage her privately you can contact her on