• The Celtic Era. This was the time when the Celtic kingdoms still existed in Ireland,   the Western Highlands  & the Isles ;  clans were being formed in Scotland. In 1242 Brian O'Neill, backed by the Norman Earl of Ulster and by the O'Donnells triumphed in battle and slaughtered King Domnhall MacLochlainn with ten of his immediate family, his chieftains and most of the adult MacLochlainn males; the MacLochlainns, for centuries Kings of Aileach and High Kings of Ireland, never again challenged their kinsmen the O'Neills for supremacy. Shortly  after the death of King Domnhall, the MacLochlainns of Cowal began to be recognized as a clan under their chief Lochlainn Mor ( Lachlan the Powerful). The Maclachlan of Maclachlan family is directly descended from this Lochlainn Mor. 

•  After 1242 the Irish MacLochlainns were a broken clan; their lands on Inishowen peninsula were lost for ever.  After being High Kings over six centuries, they were no more. About 25 years ago an Irish historian  maintained that some Irish records indicated that Lachlan Mor had fought for King Domnhal; that some MacLochlainns who fled from Inishowen took refuge with Lachlan Mor; that this became the nucleus of Clan Lachlan  in Scotland. In the conditions of the times this could have happened.  
• Over the centuries there has been a  continuous interchange of people between Ulster and Argyll. The spelling of family names have changed depending on the country of residence.  McLaughlins of solely  Irish descent  share  a common Celtic and Irish  ancestry with the MacLachlans of Clan Lachlan and if they subscribe to the objectives  of a Scottish Highland  Clan Society are welcome and qualify as members.

•  In  an unbroken line  for close to 750 years , old castle lachlan  takes us back to the days  of the Kingdoms of the Gael where in Ireland, Western Scotland and the Isles our ancestors lived by the 2,000 year old clan values and communal culture of the Celt 

• Scotland's War of Independance. The clan legend is that a  Castle was built by the Chief's Lady when the Chief was away in the Crusades.  From the records of the Scots  and the Crusades, the only candidate is the Eighth Crusade under Louis IX . This would put the starting date about 1270 and the Chief as Lachlan Mor and the Lady as one of the rich and powerful Carrick family.
• This is supported by another  legend that the Lord of Castle Lachlan and the MacArthur , Laird of Strachur , vowed that  if either was killed on the Crusades the other would bring his body back. In later years in honour of this agreement they lowered the head of their neighbour at their funeral. MacArthur was on the Crusade and there is evidence that a Lachlan Mor was  one of the leaders of the Carrick men on the Crusade. The father of Robert Bruce and Prince Edward, later Edward I, distinguished themselves on this Crusade. 
• The legend is that when Robert Bruce  in 1272 returned from the Crusades with the news of her husband's death, the redoubtable widowed Marjorie,  Countess of Carrick in her own right, detained  this virile Crusader until a marriage was consummated.; they had five sons and five daughters.  Their first son became Robert the Bruce, King of Scots. This was the period of William Wallace and Robert the Bruce when  Scotland was forged as a nation, independent of the Norman feudal system in England.

 http://www.oldcastlelachlan.com/