In 1935 Challen, one of Harringay's several piano manufacturers, built the largest piano in the world at their Hermitage Road factory. At 11 feet 8 inches long and weighing over one and quarter tons, the piano held its record till early this century.
Built to mark the King's 1935 Silver Jubilee, the piano was finished in silver and named the "great silver piano". It was first shown at the British Industries fair in the Jubilee year, where it was inspected by Queen Mary, and was played for her by Billy Mayerl.
The piano was acquired by Lord and Lady Montrous of Manchester and was used at a garden party for the Royal Family in 1936. However, because of its excessive weight apparently it sunk into the boggy ground and was later used as a garden.
See Billy Mayerl playing the piano here.
Fantastic! I own an unusual 'upright grand' Challen piano, now sadly nearing the end of its natural life. What's strange is that it was bought in Lincolnshire, then came to me in London, and now resides only a few hundred yards from the factory it was built in - as though it had a homing instinct. Would have loved to have had a tinkle on this monstrosity, or even to have strolled round it when it was in use as a garden.
This mystery was picked up by The Guardian this week who have sent out a call to try and track down the piano.
I wonder if you meant Montagu, the family name of the Duke/s of Manchester?
I just came across this article again and have found a few more clues. The press in 1935 was full of adverts for the piano appearing on this or that piano showroom as a marketing gimmick. It seemd to peter out by the end of that year. Thought it did make an appearance as a marketing gimmick in 1936 and again on 1945. Then nothing.
I did however come across the following letter published in the Liverpool echo in 1987: