In the US, when a director, officer or 10 percent owner buys or sells shares in the company they work for (insider buy/sell), a Form 4 or Form 5 must be submitted to SEC, and can be found on the EDGAR website.
What is the equivalent in the UK?
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Director dealings have to be declared to the London Stock Exchange via the Regulatory News Service (RNS).
You can search that at https://www.londonstockexchange.com/news?tab=news-explorer ; to see just director dealings, click "Filter by" and select "Headline type" and then tick "Director/PDMR shareholding" and then "Apply filters". It may be useful to also select "Index" and/or "Sector" to cut down the amount of small-cap noise depending on how broadly you want to search. Note that "Time Period" defaults to "today" and you may want to expand that.
(A PDMR is a "person discharging managerial responsibilities"; typically a senior executive who has access to inside information about the business.)
This should link to all the director dealing RNS for FTSE100 companies in the last month: https://www.londonstockexchange.com/news?tab=news-explorer&headlines=184&indices=UKX&period=lastmonth
For significant "owner" trading, you would also want to select the "Holding(s) in Company" RNS. In the UK the threshold for reporting is 3%.
Some useful background on RNS and the various types of announcment at https://www.sharesmagazine.co.uk/article/understanding-the-different-types-of-stock-market-announcements