In a dramatic statement, Minerva has scrapped its plans for it's one million sq ft tower near Aldgate, in favour of a project half the size, to be called St Botolph’s House. Although planning permission had been granted for the Grimshaw design, concern has been growing over the plentitude of new office space under construction in the Square Mile. Property market observers had long been sceptical about the viability of the “Minerva Building”. Yesterday Minerva said that its new independent value, C B Richard Ellis, had wiped £15 million off the value of the site to £110 million. However, the writedown was more than compensated for by a £30 million rise in the value of another scheme in the City — The Walbrook, a 455,000 sq ft speculative office project close to the Bank of England.Currently the city of London is bristling with cranes, raising fears that developers will overbuild. This year just 1.75 million sq ft of space is set for completion, 64 per cent of which has tenants lined up, according to GVA Grimley. By 2009, 4.6 million sq ft is set for completion, of which 4.3 million is speculative.Is the demand for office space in London declining? The question stems from the difficultly of letting office space at the Gherkin tower. Currently in the pipeline projects such as 122 Leadenhall Street (RRP), the Shard of Glass (Piano), Heron tower (KPF) and 20 Fenchurch Street (Vinoly) are still waiting to be built. But will they?