Essential morning reading is Matangi Tonga Online, of course. To that end its April 23-24, 2018 edition reported: "The announcement by Britain’s Foreign Secretary Boris Johnson on 19 April that the will be opening up diplomatic mission in...Samoa, Tonga and Vanuatu."
One could theorise that Britain’s sudden interest in establishing High Commissions in tiny Pacific islands represents a sudden burst of humanitarianism, consular care or even to counter a rising China presence. As a realist I'd say countering China is a piece of the puzzle, but there is more.
I sense a more important commercial motive, which is Britain wanting to paint itself as a returned Pacific power in order to increase its chances of selling its Type 26 Future Frigates to Australia. The sale is worth AU$35 Billion, so the incremental step of opening 3 very small, low cost, High Commissions is a good diplomatic-commercial move. Britain can claim this is one part of its return to Pacific strategy and the Australian Government can use this "we are not alone against China" line on the Australian public
I hear you scoff!
International political arguments appeal to the politicians of Australia's National Secuty Committee of Cabinet, who will choose the winner, as much as complex weapons system capability comparisons.
Remember France repeatedly reminded Australia of France’s Pacific power status on the way to selling the 12 French DCNS (now Naval Group) Submarine Project in 2016, worth AU$50 Billion. See Submarine Matter’s article 2016 Defence White Paper - Comparing Australia's relations with the 3 Submarine Contender countries of March 3, 2016 - a White Paper released just before Australia’s April 26, 2016 Buy French Submarine decision.
Avid readers of the Australia’s 2016 Defence White Paper will note the mentions of France's Pacific presence in Section 5.83 (in red and bolded here).
This British diplomatic groundwork is nicely timed, given Australia may well make the Future Frigate decision (Britain vs Italy vs Spain) before July 1, 2018. (see "Government to announce Prime [Future Frigate] Contractor" in 2nd Quarter 2018 in the Australian Defence Department’s own “Achieved/Forecast” column.
So news of the UK upgrading its Pacific presence (even in small ways) can be seen as a ship sale booster.