Alarm cable is quite thin, and therefore I would agree with Bernard Green and use bootlace ferrules and a crimp tool with heatshrink over. Chockbloc connectors are large and an eyesore, and can allow the cable to be disjointed very quickly! Owain DIYer's suggestion to use a tamperproof junction box is also perfectly valid, of course.
This is all that's inside some junction boxes and, as you say, this is a diy forum! Of course, graded systems require graded junction boxes but these won't be diy installs.
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