Another day in the Phoenix Park is always welcome, especially for any of us living more than 5 Km from there in this time of "lock down". I think I know some of the history of this house, but I am very happy to wait and read the facts you discover before I comment. I have used this strategy before and it has served me well, in that most times what I thought I knew was in fact incorrect. We live and learn! Over to you.
+++ UPDATE +++
Really enjoyable stream of comments below that I would encourage you to read – arguments about official buildings in the Phoenix Park, diplomatic relations (FURIOUS Irish Bishops!), missing conservatories, windows that don't match. Not to mention a “blood-stained coat left under the drawing-room couch”...
Photographer: Robert French
Collection: Lawrence Photograph Collection
Date: Circa 1865-1914
NLI Ref: L_CAB_02650
You can also view this image, and many thousands of others, on the NLI’s catalogue at catalogue.nli.ie
Owner: National Library of Ireland on The Commons
Source: Flickr Commons