His first major work was to suppress a minor rebliion, after which, joinjing the English barons in their struggle against John, he led an army south. However, when John's son Henry III made peace with the French prince Louis, Alexander joined in the suppression of the remaining rebel barons. Perhaps as a result, he was married, in 1221, to Henry's sister, Princess Joan of England. The two kingdoms faced a clash in 1235 when Henry demanded homage from Alexander, and Alexander demanded surrender of the northern English counties as being traditionally Scots territories. A compromise was reached in 1237 without war.
Joan died in 1238, childless, and Alexander remarried, in 1239, to Mary of Coucy (a village in northern France). Two years later their son, the future Alexander III was born.
In 1243 Henry threatened invasion, but Alexander, by stalwart readiness, and the English barons, by ennui and disinclination, made the English king resile from the scheme. Thereafter Alexander turned to trying to oust the last vestiges of Norse power in the Western Isles.
In the course of this he caught a fever, and died in 1249, in the Inner Hebrides. His son succeeded him.