I wouldn't get too excited about the O S Memoirs clearing things up....
Have been examining newspaper archives and I suspect that the Robert Lockhart will be associated with Kilroot rather than Duncrue/Duncrew. The Lockharts in Kilroot were Presbyterian (at least one was an elder)
As you already know the Tithe book of 1816 for Carrickfergus parish has , under Duncrew,
James and Robert Lockhart.
The Belfast Newsletter of 23/12/1828 has a petition to the Mayor of Carrickfergus signed by a group of residents, including a Robert Lockhart (no address).
A newspaper article of Jan 1839 has a John Lockhart in Kilroot, and another of July 1840 a William Lockhart as a juror in Carrickfergus
A James Lockhart had more than 20 acres of land in Kilroot in Aug 1851. His only daughter Mary Jane married John Thompson Jan 1877. His son James married Susan Weatherup 28/12/1871 and had Donald Weatherup Lockhart who died 18/10/1937. James senior died 26/3/1922
A Margaret Lockhart , relict of James Lockhart , Kilroot, died Feb 6, 1895, aged 78 and was interred in St Nicholas Burying Ground which therefore may contain some informative tombstones
Duncrue is in the townland "Middle Division" where the Griffiths Valuation of 1861 lists William ,John , and James Lockhart , all tenants of Marquis of Downshire (A Robert Lockhart is also listed in North St and Thomas in West St). I have gone through the Register of Deeds Grantor Index from 1860 backwards several decades and there is no record of any MOD /Lockhart lease (which didn't surprise me , but it would have been nice)
In Nov 1851 "Janet Lockhart , a middle aged woman" met a grisly end in the Bleach Works at Woodburn. She fell into machinery and was ground up.
An article of May 1852 describes
"Duncrue Salt Fields ... about a mile and a half to the north and west of Carrickfergus and opposite the picturesque village and bleach green of Woodburne"
The salt mines were a thriving concern and in Dec 1852 much excitement arose when they finally discovered coal (as had been predicted) under the salt. Hence Kilroot Power Station.
More tragedy in the Lockhart family - Belfast Newsletter Jan 31 1867:-
Report of inquest at Duncrue into death by gunshot of Mary Lockhart , a young woman of about 21. Mary and her sister (not named) were in their own house when a young boy of about 13 called Irwin, a relative, came in looking for their brother's fowling piece. The sisters indicated same and even some caps for the gun. Thinking to just frighten them and neither party realising gun was loaded he pointed same and fired. Mary was hit in the head and died instantly. Verdict of accidental death. This is after official death registration began but image is not available on irishgenealogy, however copy can be ordered and might just be enlightening about her parentage
In Dec 1902 a James Lockhart , tenant in Eden, which is adjacent to Kilroot , was in a rental dispute with his landlord W D Duncan Wilson
In 1903 James Lockhart in Kilroot acted as spokesman for tenants on Holywood estate and is probably the same who was prosecuted for not getting his son Edward McNeilly Lockhart vaccinated
I am slightly puzzled as to where your 1851 census info comes from. There are Lockharts searchable for that year on the National Archives website but not the ones you state ?
Matt
PS Just as i was about to post, I saw Aghadowey's comment about not getting your hopes up, echoing my own sentiments, amplified by this post
