Impact of CE with planned Completion later than Completion date

On an Option A contract the Completion Date is 30th June and the Contractor’s planned Completion date is 30th October. If additional works are instructed to be completed by 30th November (i.e. 1 month after planned Completion) am I correct that the Completion Date moves by just the 1 month that the planned Completion date moves (i.e. to 30th July) and not to 30th November?
Also would delay damages be applicable from 30th June or not until after 30th November?

you are correct in your assumption as the contractor is not absolved from its delay by the issue of a late instruction. This is the principle set out in Balfour Beatty Building Limited v Chestermount Properties Limited 62 BLR 1. Its sometimes known as the “dab on principle”.

Thanks Mike. What about delay damages? The Contractor would not be able to complete the additional works until 30th November (due to co-ordination with Others) so presumably delay damages would not be deductible until then, despite the Completion Date only moving to 30th July?

delay damages would be from end of June to the end of October or an equivalent period. Best. Mike