In 1845 the sisters combined their resources to build the New Castle Oliver, up the hill from where their grandfather’s house, Clonodfoy, had stood. Mary and Elisabeth chose the style of Scottish Baronial, a style popularised by Prince Albert, husband to Queen Victoria. The plans were only a few inches in size, and giving the uses of most of the rooms, are signed by the architect and dated 24th June 1845. They are in the Manuscript room of the national library in Dublin. Elisabeth, and very likely Mary, moved into Castle Oliver in 1848 and busied themselves with adorning the interiors, probably dividing their time between their new home and their other estate in England, until the following year when Mary married. A few years later Elisabeth also married to the uncle of her sister’s husband. So both sisters became Trench –Oliver wives. Elisabeth’s husband later became Lord Ashtown.
Both sisters were highly artistic. They made stained glass, painted panels on doors designed stencils and wallcoverings, and probably fabrics as well. Some of their work still survives at Castle Oliver. Lady Elisabeth Ashtown, as she was known, died on the 23rd February 1893, at the age of 81, having survived her husband by thirteen years. Having had no children together, Elisabeth left Castle Oliver to her husband’s grandson from his first marriage, the hon. William Cosby Trench. Mrs. White of Glenosheen, now in her 80s whose father worked at Castle Oliver, recalls her father mimicking his employer’s haughty manner: ‘ very Honorable he thought himself’ Mrs. White remembers him waving rather like the Queen as he passed by in his carriage, and says he used to send them delicious apples from the wall garden.
In about 1975 the last descendent of the Trench family left Castle Oliver, and it fell into a sad state. The estate had been reduced from 7,142 acres to just 15 acres. Even the entrance lodges were sold off. It is lucky that the castle survived at all, since many such building were burnt down or blown up in the troubles of the 1920s. Hopefully Castle Oliver is safe now, and will stand for hundreds of years.