William Blake famously imagined 'Jerusalem builded here' in London. But Blake was not the first or the last to visualise a shimmering new metropolis on the banks of the River Thames. For example, the Romans erected a temple to Mithras in their ancient city of Londinium; medieval Londoners created Temple Church in memory of the Holy Sepulchre in which Jesus was buried; and Christopher Wren reshaped the skyline of the entire city with his visionary...