As part of her self employment Katherine was asked to carve a plaque in Portland stone commemorating Ignatius Sancho, the first black Briton to receive the vote; this was unveiled at Greenwich Park. Greenwich Park is an English Heritage and World Heritage site. She copied the style of a neighbouring plaque by taking a rubbing of its inscription, she also gilded the plaque.
Mentioned in Wikipedia -
A plaque to the memory of Sancho was unveiled on 15 June 2007, by Nick Raynsford, MP for Greenwich, on the remaining wall of Montague House on the south-west boundary of Greenwich Park. The plaque was funded by Friends of Greenwich Park to commemorate the bicentenary of the Abolition of the Slave Trade Act, made law in 1807.