The Masqueraders by Georgette Heyer

Robin had instructions to bring his sister to Barham Court, where my lord would await their coming. My lord wrote a beautiful letter to my Lady Enderby, thanking her for her kindness to his daughter, and begging her to honour his house with her company. He purposed to invite Sir Humphrey and Letty Grayson down too; my Lady Lowestoft, and of course Sir Anthony Fanshawe. He had begun to meditate nuptials: Robin felt sure that they were to be magnificent.

As for this unlooked for ending, it took Robin's breath away. It seemed there was no longer room for doubt: the old gentleman was Barham indeed, and the days of their adventuring were over. Faith, and it was like him to allow his children to doubt him to the end! It gave him the chance to make a gesture. It had been so, Robin reflected, all through this masquerade. Simplicity was abhorrent to his lordship; he revelled in a network of intrigue; he loved to accomplish the impossible. A less tortuous man might have established his identity in a way quieter and more direct; a less fantastic man might not perhaps have perceived the need for his son and daughter to be in town all this while. They could have escaped to France, and waited there. Robin understood the workings of that stupendous mind. The old gentleman wanted them to see his triumph; it would have lost half its savour if they had not been there to be mystified, aghast, and at the last thunderstruck. He liked also to make a dupe of the whole of Polite Society. He had thrown his son and daughter right into the lion's den, masquerading in a preposterous guise: Robin could imagine his delight. In fact, the old gentleman had once more shown himself to be too clever for the rest of the world, and for him that was the breath of life.