When, if ever, is a contractor entitled to claim the 'costs of acceleration'?

This can be summed up by three simple statements:

(a) There is neither clause nor provision for this within standard JCT contracts.

(b) Contractor and employer could make a separate agreement regarding this, but payment would be non-contractual.

© Should a contractor accelerate without explicit agreement from an employer, (s)he will be highly unlikely to be able to recover the costs involved.