London, December 9 : An RSVP reached a Dorset guesthouse through Britain's Royal Mail 89 years after it had been posted.

The letter dated November 29, 1919 left recipient Janet Barrett baffled after it was dropped in her letterbox along with a note from UK's national postal service apologising for any delay or damage in the delivery of the item.

"When I first looked at it I wondered why I had been sent this tiny envelope. Then I looked closer and spotted the date, 1919. I could not believe it. Who knows where it has been all these years?" the Telegraph quoted her as saying.

A Royal Mail spokesperson admitted the delivery was a "mystery", adding the letter could not have been in the firm's system till now.

"We carry out regular checks of machinery, mail bags and post boxes to make sure items are not held up in the system," she said.

"The letter could have been a collector''s item which was being sent in another envelope and somehow came free of the outer packaging," she added. (ANI)