As I've nothing better to do for a few moments, I'll flesh out some modest figures.
For those content to live modestly on say a thousand pounds per month:
One can reasonably expect to make 8-12% on Grade B Investments (low to medium risk),
And around 50-80% overall gains on actively traded higher volume 'safe' stocks in a volatile market.
Split that 50/50 and without even considering leveraged higher risk gambling activities, you get;
(using the lower ends of expectations)
£75,000= Invested @8% returns for half.
£12,000= Traded @50% gains for other half.
Which gives an answer of around £87,000 Capital required to achieve the desired income threshold.
That's in the mid-range of the polled figures and well within the reach of a reasonably good trader/ investor with a bit of a nest egg to get actually earning some proper money instead of languishing in any old banks piss poor investment offering where the bank makes shedloads of dosh and pays out a few measly crumbs to the suckers funding it.
Just throwing some actual 'back-of-fag-packet' figures out there to add some grist to the topic,
... maybe generate some more replies to the thread.
Now the leverage has been reduced in UK for retail to 30/1 its not as easy. But still doable if you trade intraday and manage risk correctly, do not need a lot of capital. All you need to do is compound a proportion of gains.