VC10 K4 ZD230 succumbed to the scrapman's axe a couple of years ago.
She was originally built as G-ASGA for BOAC and flew on 7 May 1964. This airframe was first example and prototype of the Super VC10, the largest jet aircraft ever built in Britain. In recent years at least, she must be a contender for the most historically significant aircraft to have been simply cut-up, with no thought of preservation.
How about individual airframes with the most hours? The VC10 fleet has some with over 50,000 hours. The TriStars must be up there too.