What's the point of the Government Office for London?

Since devolution occurred and the Government restored the GLC under a different name, virtually all London policy has been directed out of the GLA through the Mayor. The centralisation of power away from the Boroughs has, as is well documented, been slowly eroded, in conjunction with the Council tax precept* that the Mayor demands from each Borough.

Even though power in London resides in the GLA and the Mayor's Office, there remains, for some bizarre reason, a Government Office for London which apparently "represents central government across the capital, delivering policies and programmes for ten central government departments in a joined up way, and making London’s case in Whitehall."

If you take a look at their website they apparently play a significant role in areas which are actually either in the control of the Mayor, the GLA and in some cases the Boroughs. I guess this is what "double devolution" means in practice? Multiple offices and authorities with remits in the same area. And how much does all this doubling up of power and roles cost the taxpayer as a whole? Well, running the Government Office for London costs on average £15.8m a year, and it employs 268 civil servants.

You may notice that on the front page of the website it says that there is an efficiency drive to save costs and reduce staff, and it's true that it has reduced staff numbers since 2004. However, in 1999 it had 122 more staff with a headcount of 390, and cost half million pounds less to run than it does this year, this could be explained away by inflation probably, but for 2002. In that year it had just eight less staff than it has today and cost £2.3m less to run.

Personally, if we're going to keep the GLA and the Mayor in London, I don't see what the point of the Government Office for London is when all it appears to be doing is replicating work at a unnecessary cost to the national taxpayer. Unless of course devolution is really a sham?
* The precept is why Council tax is so high in London these days. The Councils' know what they need, but then Livingstone demands a slice. This results in the Council adding his share on top of it's requirement.