Bolted?

This plinth is in London's Cavendish Square, but the equestrian statue of the Duke of Cumberland, apparently erected in 1770, seems to have done a "Shergar".
I did a bit of surfing to try & find out what became of it. It seems it was removed in 1868. One theory is that as Queen Victoria was enamoured of all things Scottish, a figure of the man whose crushing of the Jacobites at Culloden had earned him the name "Butcher Cumberland" may have been deemed insensitive.
But he had been supported by non-Jacobite Scots, & surely the inscription would have remained an issue?
I found the truth in the Jan 20th, 1912, edition of "Notes & Queries". The statue was removed by order of the fifth Duke of Portland, as it was in poor condition, & melted down. The value of the metal was paid to the Treasurer of Cavendish Square to provide a new statue. The plinth is still waiting.
Now the mystery is what happened to the money!