Why did the chauffeur come to the Gubber house?

The chauffeur came to deliver a hand written message from the Duke of Hampshire.

The chauffeur unfolded the letter and began to read, "'Dear Sirs, I saw your notice as I drove by this morning. I have been looking for a decent window-cleaner for the last fifty years but I have not found one yet. My house has six hundred and seventy-seven windows in it (not counting the greenhouse) and all of them are filthy. Kindly come and see me as soon as possible. Yours truly, Hampshire.' That," added the chauffeur in a voice filled with awe and respect, "was written by His Grace The Duke of Hampshire in his own hand."