While the overall trend ha been upwards in house prices, especially in the south east, over the sorter term there have been times when properties have lost value.
Younger people find it hard to get their heads round, but the crash at the end of the 80s was awful.
It was a perfect storm of overheated housing market, recession and rising interest rates. A change in the rules about tax relief on mortgage interest created a mad moment where everyone was desperate to buy before the new rules came in, and prices rose exponentially. Then they plummeted.
At one point, there were hundreds of repossession hearings in the courts every week. People who lost their homes were often in negative equity and were never able to clear the balance of the debt. Prices took a long, long time to recover to pre-crash levels.
A couple of months before the crash, my house was valued at £87.5k, A few months later, I wouldn't have been able to sell it for half that. I eventually sold 4 years later, for £49k, and it took several more years for prices to get back to what they were. I was fortunate in that I was able to rent the house out when I relocated, the rental income more than covered the mortgage, and I was able to rent cheaply in my new town.
I know that tighter lending criteria make it harder for people to buy, but they will (hopefully) mean that something like that never happens again.