
From zx81stuff.
Lost Island is related to both Katakombs and Super Spy which both made recent appearances here, insofar as it was distributed by a British company that spawned up in 1981 only to go poof a few years later.
JRS Software started with a ZX-80 “Programmable Moving Display”, which describes itself in terms of extreme programming.
Great care has been taken so that the processing of your codes can always be interrupted to return to the display routine at the precise microsecond that is required to ensure that your T.V. picture remains completely rock-steady.

Synch Magazine, October 1981. Based on the flashing that happens on every single keystroke in Planet of Death, this is perhaps an impressive feat.
They’re located in yet another completely new spot on England, and so far throughout 1982 I feel like we’re throwing darts at random.
By ’82 in the United States you had the software market started to get centered around a few locations (especially in California) but the UK not only was behind a little in timing but also by my reckoning had a longer period of amateur publishing, especially given the prevalence of tape. So companies could still be nearly anywhere on the map. (But also, to be fair: smaller country.) To emphasize what I mean by amateur, in 1983 JRS Software published a gambling game originally by “E. Smith Software” entitled Roulette. Here is what the outer tape packaging looked like:

From ZXArt. I mean, maybe the hand-drawn marker was done later by the owner of the tape, but even without that this is very bespoke packaging. (ADD: According to Gareth in the comments, the website ZXArt which I was using likely linked JRS to E. Smith in error. This is still a sterling example of amateur publishing practice.)
Circling back to 1982, JRS produced a random grab-bag of utilities and games, but for our purposes we are interested in their single adventure published, Lost Island.

Sinclair User, May 1983.
Yes, only one, just like Golem with Katakombs! I was recently listening to the They Create Worlds podcast about Rogue, and learned that both Michael Toy and Glenn Wichman wrote text adventures (that no longer exist) before Rogue. I have the suspicion that a lot of programmers of the time wrote personal text adventures projects now consigned to oblivion. Given the prevalence of low-budget tape publishing in the UK some of these projects which normally might have ended in the bit bin could end up on tape instead. Here, the project is by a “M. Holman” who makes their only appearance in gaming history.
The premise is simply to escape the island you are shipwrecked on. Escape is the second most common plot in this era after Treasure Hunt. What’s curious is (as I’ll explain later) that approaching the game with a Treasure Hunt style mindset can actually hinder one’s progress!
I’m pretty sure the parser here is entirely of the author’s design because it has some oddities particular to this game. Verbs must be typed in full (so no INV instead of INVENTORY) but nouns can be shortened, so you GET COC in order to get a coconut.
Objects are not described in the room description unless you LOOK. At least it isn’t a Omotesando situation where the objects don’t even exist beforehand, but this still makes for an erratic and confusing UI experience and there’s no compelling reason to make the player type LOOK in every room.

Notice the room description repeat; this is where I typed the command LOOK in order to see the spear.
The spear above is interesting insofar as the game tries to stick with “on a real island” objects — that is, no magic wands — but also takes this a bit farther and includes objects that don’t get any use in the game. You can tote the spear above if you want but it serves no purpose, as does a musket you find later. Red herrings wouldn’t normally interfere too much with gameplay, but the inventory limit of 6 ends up popping up more than once so there’s some genuine consideration of “what do I really need?” This gives a different gameplay aura than inventory limits on most games of the time; discarding a gun as useless has a narrative sense of someone desperate for escape. When a game’s narrative instead involves dragging every item on the map into organized piles, it doesn’t come off as a narrative at all as much as the player pretending to be a pack mule.
In some cases, the game inadvertently lets you know what’s useful, because it will have an object described by LOOK that still can’t be referred to even it is there. I suppose this cuts down on the herrings while still allowing a secret cave with a telescope and a hat (you only need the telescope).

You only need one of these things. Neither “RUM” nor “CASK” is a word that is recognized by the game.
The main objective, although it isn’t clear at first, is to set a signal fire and then wait for a ship to arrive. I have it located on the map below at (END).
For the start of the sequence, you take a sword at (1) to some nettles at (2) and chop them away.

Here, the noun “nettles” is not a separate object but part of the room description that you have to assume is able to be targeted. There’s also a random palm tree you can climb (with a rope on top) with a similar issue nearby.
This reveals a cave (3) you can reach with rope that lets you get a telescope, and a cave at (4) that is blocked by rubble. It is possible to remove the rubble but more items are required.
Here I was stuck for while, although I hadn’t quite realized EXAMINE was a verb that occasionally worked yet. At a “large idol” (5) near a village with “skulls” (and yes, they eat you if you try to go in, sigh) I found a “LEDGE IN THE ROCK FACE DIRECTLY ABOVE THE IDOL” by using EXAMINE IDOL. This (via re-use of rope) let me get into a cave area with a tinderbox (6) and a snake (7).
You can KILL SNAKE as long as you have the sword with you. (If you are holding the spear the game just claims you can’t kill the snake with your bare hands.) This gives you access to a spade (8) which lets you take it back to the beach at (9) and dig up a chest, as shown in the earlier screenshot, with GUNPOWDER, GOLD, and a RUM CASK.
Remember, this isn’t a treasure hunt! The useful item is GUNPOWDER. (I mean, you can take the gold with you. It just makes the inventory more annoying to juggle.)
The gunpowder can be dropped off at the cave with rubble (the right verb is LEAVE, DROP isn’t even recognized!) and then lit using the tinderbox. (Not a torch that you can light with the tinderbox. The game may have realistic objects but it is wobbly about realistic alternate uses.)
With the cave blasted open you can find some lamp-oil (10). This lamp-oil can be poured on the signal fire (END) and the fire then lit with a tinderbox. Then you need to use the telescope to SEARCH SEA. This last bit would have likely caused me enormous trouble but I ran into it by accident earlier — I was standing at the signal fire testing out verbs and objects, and realized that if I tried the SEARCH there the game said “I CAN”T SEE FAR ENOUGH”, and that was the only location where that message happened. This made me realize it had to be the spot where the telescope was useful, so once I got the fire going I just started to use SEARCH on every noun.
With the ship’s arrival, you can then just take a couple more steps to victory. No treasure is required.
This game emphasized for me the varying-talents hodge-podge that authors at the time had. Some authors could pull off a relative sturdy parser but had questionable design choices; some had good idea but had trouble conveying them. This game falls into the latter, insofar as communicating was a consistent struggle (and remembering to always LOOK, and to check EXAMINE and SEARCH on nouns that might not even exist) but having a “realistic” series of obstacles and having treasures that should be ignored in favor of the overall goal was a refreshing idea.
If you’re interesting in testing the game out, it is playable online at zx81stuff.

Ok, this is mostly irrelevant, but I have to show this. Here’s the actual tape of Roulette, with everything hand-done in marker. I’m fairly sure this is a case where the author genuinely only published 30 tapes or so (dropped at a local computer outlet or taken to a show) and drew on all of them by hand.