18th December - Royal Mail 2nd Class (free on orders over £10).
21st December - Royal Mail 1st Class (£1.99 on orders over £10).
22nd December (by4pm) - Royal Mail Guaranteed Next Day by 1pm (£9.50).
Please note that due to Covid, Royal Mail does not absolutely guarantee that either 1st or 2nd class will be delivered in 24 or 48 hours respectively (in our experience though 98% of our orders are arriving on time). Only the Royal Mail Guaranteed Next Day by 1pm service is guaranteed.
*Update (9am 21/12/20): Royal Mail have announced:
"In light of the changing coronavirus restrictions announced on Saturday 19th December 2020, we have made the difficult decision to make the following changes to our timed guarantees for our Special Delivery by 9am and 1pm services:
For Special Delivery Guaranteed by 9.00am and Special Delivery Guaranteed by 1.00pm items posted on Wednesday 23rd December we are suspending our delivery guarantee.
While we cannot currently provide a guarantee that items posted on Wednesday 23rd December will arrive prior to Christmas due to the impact of the new coronavirus restrictions, we can assure you that we will be endeavouring to deliver all items as quickly as possible. We know how important this is.
Special Delivery Guaranteed by 9.00am and Special Delivery Guaranteed by 1.00pm items posted up to and including Tuesday 22nd December remain unchanged.
Read more at: www.royalmail.com/coronavirus"
This means that we can only guarantee that orders placed by 4pm on the 22nd December using Royal Mail Guaranteed Next Day by 1pm will arrive by Christmas, not the 23rd as previously stated.