Last year, the rare stamp auction markets were dominated by the Chartwell collection, a gargantuan hoarding of British and British Empire stamps collected by Sir Humphrey Cripps and offered by a London auctioneer across a series of record-breaking auctions.

We wrote a top five of our favourite stamps sold, and one of them was the most valuable philatelic sale of the year.

But, it's not over yet. Next month sees the opening of the Chartwell collection of Line-Engraved Essays and Proofs, part II.

Here's a quick taster. We will of course be presenting you with all the highlights over the next few weeks.

One of the key lots is an 1840 wonderful die proof - one of just two which remain in the hands of collectors.

In January 1840, the details of the stamps which were later to be the Penny Black and Twopenny Blue were still very much to be fixed.

Chartwell collection 1840 five column comparison experimental engraving plate

This item was made from an experimental plate made for comparison of the two backgrounds. It was also intended as method of testing out spacing. The piece is made up of two rows, each of which has five impressions in blue.

Printed on a single sheet of India paper, it is listed at £120,000-150,000. We're currently privileged to hold another wonderful example from the early stages of the development process in the form of a Great Britain 1840 Rainbow Trial plate of twelve.

This is the only known example in private hands (another is in the Royal Philatelic Collection), and should be considered an excellent opportunity to gain a unique piece of philatelic history.