Philip was surprised by the standard practice of excluding sunk costs already spent, when deciding whether to continue with a scheme. Half of those sunk costs are NOT excluded in this case as DfT has accepted an estimate of “the cost of remediating work [after] a possible cancellation – £11bn in 2019 prices” Again standard practice NOT “creative accounting”, when deciding whether to continue.
The outturn BCR of HS2 Phase 1 is most likely to be negative if Phase 1 doesn’t reach Euston. It’s not important in its own right at this stage, but incremental BCRs are, leading to the question I posed “As the latest uncommitted cost is £13.3bn-£19.3bn,.. are the faster services to Birmingham and the capacity relief to the WCML worth up to £19.3bn in 2019 prices? DfT & I say yes.

The latest expected cost of Phase 1 as originally proposed is £49bn-£57bn in 2019 prices. That implies Philip’s £100bn figure in outturn prices is a little of an overestimate. Part of that likely outturn figure has been caused by stopping and changing the project, which usually increases costs rather than reduces them.
Often it is better to agree to omit some aspects at agreed nil cost and then pay separately for the alternative works. That needs to be assessed for the Euston approach tunnels, if HS2 Euston is indeed reduced to 6 developer funded platforms. 6 platforms works best in the 2060s if a few HS2 8 or 12 car trains can be diverted to WCML platforms. So the third tunnel needed for 10 platforms will still be needed, but in a slightly different form.
As regards the assumptions on the cost of fares. HS2’s BCR have been calculated based on current fare levels in the standard way. Extra generated passengers are regarded as saving half the time of existing passengers. We know they don’t travel now, but do travel at the reduced journey time; some would travel if journey times were reduced by less and some wouldn’t; A classic triangle of benefits and a standard formula to calculate the area of the triangle as well as the extent to which fare income generated exceeds the operational costs.
Irrespective of whether “this project should never have been started”, we are where we are and we should take considered decisions – including estimating “the cost of remediating work [after] a possible cancellation” and paying for breaches of contracts.

HS2 isn’t about cutting the time. Why don’t you know this!?

Giving a civil engineering a cost plus contrac, unbelievable

What absolute drivel. Designers don’t need to be on site unless for a very specific reason. Clearly you have zero clue on modern engineering design. Stick to digger Boomer.

But someone says outturn cost at over£100 bn. Not a good result!?

So the contractor doesn’t take all the risk and may make some money! That’s so unusual as to be worthy of comment!!

Oh, dear! Just kick the contractor who’s out there in the wind and the rain trying to make sense of it all!! Interestingly, the designers took a kicking this week. A year of the delay due to designers ‘working from home’. They probably didn’t even visit the sites, just went on Google Maps! Please remember, someone’s got to turn your rough sketches into reality!