Building’s leader (23 March, page 3), while welcome, went nowhere near challenging the government’s apparent confidence in the latest cost estimates of the London Olympics.

Building professionals will know all about smoke and mirrors when it comes to estimating a cost ceiling at this stage in the development of a scheme of this magnitude. A competent QS might have a chance of approaching the truth at final design stage, but we are far from that point. Even then, substantial doubt would remain and the accuracy of his estimates would depend heavily on the state of the construction market at that time.

Supposing “firm” quotes were obtained – an unlikely scenario – the client’s budget would still not be secure. The accuracy of “lump sum” quotes depends on the finality of the brief, whether the client will change its mind during construction and how complete the design is at tender stage – not speculating on the likelihood of successful claims. So just why the government, having secured the honour and prestige of mounting the 2007 Olympics, won’t admit at this early stage that it has no idea of how much it will cost, I cannot understand. Whatever figure it comes up with between now and the end of construction, there will be some red faces.

Malcolm Taylor, Tanglewood, Lancaster