HELP - Water proof wire connection

[olderdan]

With winter right on us I realized that my driveway lights are out. Getting home at after sunset and lights on a daytime switch.

When I installed them some 5 years ago I used what we call twin and earth cable...1.5mm sq is good enough to drive the 6 x 60Watt globes spaced equally distant down the drive way.

Upon investigation I found moisture had gotten into the joints where I tapped off to run a supply to the individual lights. On hind sight I should have taken the cable up the post and made the joint above ground at the light fitting, but for now I am stuck with having to mage the joint at the base of the post and subsequently partially under ground.

I used valcanising tape to ensure a waterproof joint but clearly this could not stand the test of time.

I need some proven ideas how to make a lasting waterproof joint. the wire is a single strand copper wire, 1.5mm sq

You probably know this already but that vulcanizing tape has to be stretched to 2 thirds of its width to seal properly, I would redo the joints the same way and add a silicone tube injected with low modulus silicone as a cheap fix , there are underground jointing kits but they are quite expensive.