On his way to England, Claude made friends with his captors. By the time they reached London, Claude and the Kirkes were on such good terms that they introduced him to the English King Charles I. A the same time, Claude met one of the queen's attendants who quickly became his third wife.

That marriage may have helped Claude to decide to switch sides in the struggle for control of Acadia. He made a deal with Sir William Alexander, who held the English grant to the land. Claude would help Alexander establish a colony in Nova Scotia and would prevail upon his son to do the same. In exchange, they were to be given land there and were to be made Knights Baronet of Nova Scotia.

Claude thought he had joined up with the winning team and that he could influence his son to do the same. Events would eventually prove him wrong on both counts.

Claude sailed to Nova Scotia in 1629 with Alexander's eldest son, who was also named Sir William Alexander. There were two groups of settlers with them. One group, led by Claude and the young Alexander, settled on what would later be called the Allain River at a place they named Charlesfort. It was also called Scotch Fort, and was less than five miles from the all but abandoned French settlement of Port Royal. A second group, led by Lord Ochiltree, settled on Cape Breton Island at a place they called Baleine. Later, when the French built a fortress at the site, they called it Louisbourg.

Baleine would not last very long. In August 1629, Captain Charles Daniel, an officer of the Company of New France, set up a fort at St. Ann's Bay on Cape Breton Island, established a garrison of French soldiers there, and then marched against the Scotsmen. On September 18, he overran Baleine and captured everyone there.

But, with Claude de La Tour's help, the Scots were able to dig in at Charlesfort and to hold their ground. In recognition of his efforts, Claude and young Alexander signed an agreement at Charlesfort in October 1629 in which the La Tours, father and son, received a share of the fur trade and a strip of Nova Scotia's Atlantic coast. Claude went back to English in early 1630 and the grant was formally awarded to him by the senior Alexander on May 10, 1630, "upon condition that the said knight (Claude) de la Tour, and his said sonne, as he hath promised, and for his said sonne by these presents doth promise to be good and faithful vassals of the Sovereign lord the king of Scotland (who was Charles I of Great Britain)...and give unto him all obedience and assistance to reducing the people of the country."

Claude sailed back to Charlesfort in the spring of 1631. On his way, he stopped at Cape Sable to tell his son about the deal he had made for both of them.

There are several accounts of what happened next. Charles Mahaffie reports, "There are two reports of the father-son reunion....In his version published in 1632, (Samuel) Champlain says that Charles 'had not allowed himself to yield to the persuasion of his father, who was with the English; for he would rather have died than to consent to such baseness as to betray his king.' The other account is by a friend of Charles' named Nicolas Denys, who years later wrote a history of Acadia in which he relates Charles' response 'that he was under great obligation to the King of England for so much good will towards him, but that he had a master able to appreciate the loyalty which he owed to him, and that he could not deliver the place into their hands, nor accept any commission other than that which he held; and he thanked the King of England for the honor which was done him, but that he could not accept any rewards except from the King his master.'"

Some of the versions attribute Charles' refusal to loyalty to France. Most say it was simple pragmatism: He disagreed with his father about which side would ultimately win the struggle for control in Acadia.

According to several accounts, father and son took up arms against each other after Charles refused to go along with his father's deal. Those accounts say the Scots tried to force Charles from his stronghold at Cape Sable, but that he successfully resisted. Other accounts make no mention of fighting, saying only that when they were unable to persuade Charles to join with him, Claude and his Scotch friends boarded their ship and sailed on to Charlesfort.

Whether there was fighting or not, father and son reconciled some time before 1635. Denys reports that in that year Claude and his English wife were living at Cape Sable with Charles and, "very amply provided," they lived out their lives in a home that Charles built there for them.

 By that time, Claude's dealings with the England had become moot, since Acadia was, at least for a time, back in the hands of the French.