In large part because England has always had a larger population. The lowlands are much more practical for large communities than the highlands. It's easier to farm, and there is better access to rivers. The fact Scotland's people were also more divided (most of the time) helped as well. Today the population divide has grown even more stark. Scotland's entire population today stands at less than five and a half million, while England has a population of over 50 million.

Larger more unified population means more tax revenue, and bigger and better equipped armies.

How are we defining powerful?

In pre-Roman Britain, the ideas of the current nations of the United Kingdom did not exist. No England, Scotland or Wales. All were broadly Brittonic peoples with no nationhood. I'm not at all sure how one would describe one people (Picts, Celts etc) as more powerful than another.

In Roman Britain, the areas now knows as England and Wales were part of the Roman Empire and it is probably safe to assume that the Empire was more powerful by any measure than any of the pre-Scottish peoples.

In immediately post-Roman Britain, the notions of England and Scotland STILL didn't exist. In the area you are interested in, I am not sure how you are defining relative power. The power of the old Knigdoms I would have thought is to be largely taken in their context i.e, their immediate neighbours.

Minor Kingdoms were swallowed up until Wessex, Mercia and Northumbria were the truly powerful 'political' units. Perhaps this is the point at which you could say people living in what is now England were more powerful than those living in what is now Scotland. I would suggest that it was a case of the richness of the terrain and the relative closeness to Europe bringing about a stronger economy and population growth. Most of Scotland was still wildly rugged and parts of what is now England, remarkably well connected to the rest of the world.

By the time we get to a notion of England, Alfred the Great and all that, the Vikings were very much on the scene (had been for a long time) and in fact ruled vast swathes of Britain in an area known as the Danelaw before Alfred was known as "the Great".

The resistance to the Danes and the prevailing of Wessex gave rise to the beginnings of England. By this point I would suggest that England was more part of what then might have been described of as the "developed" world and perhaps crucially, Christendom. The agricultural land and climate in what is now England being capable of generating immeasurably more wealth than the only agriculturally useful parts of what is now Scotland.

With greater production came the idea that some people could make a profession out of fighting. The king and his lords had retinues of dedicated warriors (huscarls/housecarls and their retainers). This could be paid for by a ruling class that could raise taxes from their very rich farmland and not everyone was needed in the fields because farming in fertile England was far more productive. At the time, I would suggest that Scottish warfare was largely carried out byt the same people who had to be back in the fields come harvest and probably didn't get much time or equipment to practice killing eachother.

The vast bulk of the fighting men in any conflict still came from the fyrd (drafted landspeople, not warriors) but I think that England was developing the profession of fighting wars and had the economic muscle and people power to mine iron, beat out swords and make armour.

I think that this set the tone for the next few hundred years. Scotland has never been as populous and a quick browse on wikipedia yields the following: "Scotland has only between a fifth and a sixth of the amount of the arable or good pastoral land of England and Wales and most of this is located in the south and east." It stands to reason that England was, at a time when everything was based on agriculture, always richer.

Also, Clans and their importance survived in Scotland well on in to the medieval period and so a cohesive military force must have been hard to put together with every Campbell wanting ever McDonald dead in a ditch and the other way around.

I am not a historian, I just have a really keen interest in history (and am British) and all of these assertions are just based on distilling my own reading around and visiting sites all over my home country.

In short - I don't know how you're defining power. I don't think it's necessarily true to say that "England" was "more powerful" than "Scotland" in the times you specify because the nations were far from existing yet. I think England became a more truly 'medieval' society much earlier than Scotland did and with this era came technology, economic power and a politcal system that made it possible to mobilise a country (providing you had the loyalty of your lords!) I don't think this happened in Scotland until long after and possibly never did to the same extent with Scotland retaining its distinctive clan culture well in to the true wars between the two nations. England was rich, advanced and more choesive. Scotland, sure to its terrain, location and overhanging pre-medieval culture, was poorer, had less technology at its disposal and was still as fractious as ever.

This makes me miss history lessons! The more I type the more I find it interesting that maybe you could describe Scotland as taking centuries longer than England to become a medieval society. But then it sort of was forced on the English by the Normans... That's another thing!

Nah, I won't ramble on about that. But it is worth noting technology/power-wise, the Normans 'modernised' England forcibly, making it truly medieval and linking it inextricably with mainland Europe giving us knights and castles and so on. They did not conquer Scotland and have the same effect. Immediately after the Norman invasion maybe you could say comparing England and Scotland was like comparing Medieval and Dark Age.

The starting point is geography. The north of Britain is generally less fertile, more rugged, and endowed with fewer natural resources (in historical terms) than the south. I'll call this northern area "Scotland" from now on, for convenience, and gloss over the historical inaccuracy and the way the precise area I'm talking about changes.

Lower fertility meant a lower and/or less wealthy population. It's also worth noting that Scotland was less suited for raising horses, that key military technology.

Rugged terrain made travel and communications more difficult. This contributed to the area being difficult to conquer, but made economic and political unification more difficult.

Scotland was also further away from the main centres of European power and wealth.

The people in Scotland were more able to resist the Roman Empire. In this sense they could be judged more powerful than Southern tribes, although you could easily argue the rest of Britain was better off as part of the empire.

The period from the decline of the Roman Empire to the Norman Conquest saw a struggle between the Saxons, the Scandinavian and the Western-European spheres of influence. The North of England generally fell into the Scandinavian sphere of influence, and the balance of power shifted back and forth.

The break point came with the death of Edward the Confessor and the fight for the throne between Harold Godwinson, Harold Hardrada and William the Bastard (loosely, Saxon, Viking, Norman). Had Hardrada defeated Godwinson I think it's conceivable that Britain could have been divided even more permanently between a Scandinavian north and a Norman south. You'd need a better historian than me to answer that question though.

The victory of the William and the Normans had several effects. One was a centralisation of power. The Norman Kings of England certainly had trouble controlling their barons, but they had an easier time than the French kings. One reason among many for this is that the Norman nobility were 'imported' and distinct from the population they ruled, rather than having historic regional loyalties and enmities, that might be shared with the general population. The Normans also brought up-to-date military technology, and a social system better able to mobilise and control military force.

It's vital to note that for centuries lands in (what is now) France were more or equally important to the kings of England as those in England. They drew much of their power and prestige from these lands. To me the intermittent wars with Scotland seem like they were something of an annoyance for English kings who really wanted to be fighting in France.

My knowledge of medieval Scotland is very hazy, but I would caution that it is not necessarily what you think. Scotland didn't undergo the same social and political transformations as England, but it wasn't static. It was, for obvious reasons, an ally of France, and France had an important influence, at least on the elite. That caution aside, I don't think anyone would disagree that Scotland remained more politically fragmented than England. Scottish nobles were co-opted into the English system a lot more than English nobles into the Scottish.