The Sundial Paradox

This is the sundial and sculpture at Hill of Tarvit Mansionhouse.
The building faces southeast and the hour lines take account of the location. The sundial is not illuminated after 4:00 p.m. 

There is a paradox. The position of the house is recorded by Latitude and Longitude.
The Latitude is correct.
The Longitude is correct and incorrect and that is the Paradox!
This puzzled me and I resolved the matter.

The Longitude is correct when the meridian is the Gregory Meridian and wrong when the meridian is the Greenwich Meridian.

The Gregory Meridian 

The Greenwich Meridian is 2 degrees, 47 minutes to the East of the Gregory Meridian.

This sculpture and sundial were made and put in place about 1905. The Greenwich Meridian was internationally agreed in 1884.

Yet Frederick Sharp referenced the sundial to the Gregory Meridian. Why?

I can find no definitive reason for the decision but I can make an educated guess.

Frederick Sharp bought the Wemysshall Estate in 1904. He built the Mansionhouse between 1904 and 1907.

The Estate dates back to the 15th century and Wemysshall House was built in 1696. Frederick Sharp demolished the original building in 1904.

Prior to Wemysshall is another building: Scotstarvit Tower.
Frederick Sharp removed the fireplace from Scotstarvit and located it in the Billiard Room of his new home. The date on the fireplace is 1627.

The establishment of the Greenwich Meridian marked a significant for the Sharp family businesses.

He was cognisant of the Gregory Meridian and referenced the sundial accordingly. It was a puzzle for his friends, clients and guests to discuss and solve.

Dates feature throughout the house. The Dining Room ceiling features the date 1905 and the initials of FS and BW worked into the complex ceiling decoration. Another talking point.