I suspect, however, that the thing that confuses you about Ian is that he's half...

I suspect, however, that the thing that confuses you about Ian is that he's half Scot. In many ways he's more Scot than English, which accounts for what you're calling a ruthless streak. He'll do what he pleases, when he pleases, and the devil fly with the consequences. He always has. He doesn't care what anyone thinks of him or of what he does."
Pausing, Jordan glanced meaningfully at the couple who'd paused to look at a shrubbery on the front lawn. Ian was listening to Elizabeth intently, an expression of tenderness on his rugged face. "The other night, however, he cared very much what people thought of your lovely friend. In fact, I don't like to think what he might have done had anyone actually dared to openly insult her in front of him. You're right when you aren't deceived by Ian's civilized veneer. Beneath that he's a Scot, and he has a temper to go with it, though he usually keeps it in check."
"I don't think you're reassuring me," Alex said shakily.
"I should be. He's committed himself completely to her. That commitment is so deep that he even reconciled with his grandfather and then appeared with him in public, which I know was because of Elizabeth."
"What on earth makes you think that?"
"For one thing, when I saw Ian at the Blackmore he had no plans for the evening until he discovered what Elizabeth was going to do at the Willingtons'. The next I knew, he was walking into that ball with his grandfather at his side. And that, my love, is what we call a show of strength."
She looked impressed by his powers of deduction, and Jordan grinned. "Don't admire me too much. I also asked him. So you see, you're worrying needlessly," he finished reassuringly. "Scots are a fiercely loyal lot, and Ian will protect her with his life."
"He certainly didn't protect her with his life two years ago, when she was ruined."
Sighing, Jordan looked out the window. "After the Willingtons' ball he told me a little of what happened that long-ago weekend. He didn't tell me much-Ian is a very private man-but reading between the lines, I'm guessing that he fell like a rock for her and then got the idea she was playing games with him."
"Would that have been so terrible?" Alexandra asked, her full sympathy still with Elizabeth.
Jordan smiled ruefully at her. "There's one thing Scots are besides loyal."
"What is that?"
"Unforgiving," he said flatly. "They expect the same loyalty as they give. Moreover, if you betray their loyalty, you're dead to them. Nothing you do or say will change their heart. That's why their feuds last from generation to generation."
"Barbaric," Alexandra said with a shiver of alarm.
"Perhaps it is. But then let's not forget Ian is also half English, and we are civilized." Leaning down, Jordan nipped her ear. "Except in bed.