It is true what you say and demonstrated by where the TBM will inevitably start - at the London end. There is a congestion problem at Paddington in the West an

It is true what you say and demonstrated by where the TBM will inevitably start - at the London end. There is a congestion problem at Paddington in the West and with St Pancras/Euston in the north of London. So even if HS2 only gets to do its work at the London end before politicians cancel it then this part of the north-west London will be done, unblocking access to London for express trains. If they started in Birmingham and got cancelled they would not get this bit done. There is also property speculation to consider, already far out places like Reading are now more accessible for London due to HS2, driving up house prices. A half completed HS2 that doesn't get to Birmingham will have a similar effect.