Life was not all free and easy here before William the Conquerer.
The Celts had slaves, and if that's not 'property' and 'ownership', I don't know what is. So did the Vikings, who settled in parts of the British Isles... Early Celtic laws describe family land-ownership. They also describe customary rights to make use of 'wild' resourses (fish, deer etc) but only so long as the interests of others were not damaged
In England, Anglo-Saxon lawcodes make frequent references to land ownership and theft (especially of livestock), which shows that they had a concept of property avalon.law.yale.edu/medieval/saxlaw.asp They also had a very strong concept of obligation to community/society. There was considerable pressure to behave according to the law.
The New Statemen article mentioned above makes very valid points about grossly unequal 19th century conditions, but, even before industrialisation and Inclosure Acts there was no golden age further back in which everyone had a fair share of the land. There was actual famine in Scotland in the 17th century among people living with access (and rights) to make reasonable use of wild land. And, sad to say, quite a lot of the people who moved into cities in the 18th/19th cent did so because they were pitifully poor in the countryside. I'm not saying that was fair - clearly it wasn't - but it's how it was.
Scottish law is different from English, as previous posters have said, but a lot of it is surprisingly recent, not harking back to some misty Celtic twilight. en.wikipedia.org/wiki/History_of_Scots_law Land law, in particular, was overhauled in 2004 - if you want to know in detail how: www.ejcl.org/83/art83-5.PDF
Yes, some very, very bad things happened during the Clearances in Scotland, but the principle of ownership or tenancy of land existed long before then. Of course, it was not applied justly or fairly - as the book mentioned above says, 'the poor had no lawyers'. But even before the Clearances, common land was not open for anyone to grab and take over and use as they liked; it was managed by a network of local customs. Today, common grazing land attached to crofting communities is still managed by communal agreement. Modern community buy-out schemes also carefully manage their communal land.
Some Scottish Common Good lands (different from common grazings) are still under threat www.theguardian.com/uk/2012/jun/12/scottish-people-losing-common-land
The law of common land in Scotland is about to be reviewed: news.scotland.gov.uk/News/Common-Land-to-be-reviewed-21de.aspx