Royal mementos collected by a loyal servant during his 51-year career are expected to fetch £500,000 at auction today - more than twice the original estimate.

A letter from the Queen Mother instructing that Dubonnet and gin be packed for a day out, “in case it is needed”, fetched £16,000 this morning and almost £20,000 was paid for a collection of letters written by Diana, Princess of Wales.

The personal notes written to William Tallon - affectionately known as Backstairs Billy for his role as Page of the Backstairs - went under the hammer along with hundreds of other royal mementoes.

The auction, run by Reeman Dansie, in the unlikely setting of an industrial estate in Colchester, Essex, was being held following Mr Tallon’s death last November.

Many of the items listed early in the sale, including Christmas cards from the Queen Mother to Mr Tallon, were snapped up by bidders in a packed auction room at about £60 each.

But when it came to the most sought-after pieces, they could not compete with those following proceedings via the internet or telephone.

The most frenzied bidding in the early part of the sale, set to run until about 6pm, centred around the fascinating hand-written note from the Queen Mother to Mr Tallon.

It listed instructions including: “I think that I will take two small bottles of Dubonnet and gin with me this morning, in case it is needed.”

The note continued: “It is a beautiful day, could we have lunch under the tree - one could have fourteen at the table and four at a small table.”

Bidding for the letter, which had been expected to fetch £200 to £300, started at £1,100, drawing gasps from the audience of about 400.

But by the time telephone bidding war had reached £16,000, spontaneous applause broke out.

Just before closing the bidding, the auctioneer jokingly asked the room if there were any more bids, quipping: “It’s only money.”

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