Plus Four developed a slow puncture. Stainless wire wheels. Air is escaping from a spoke nipple ( behave yourselves!).
Phoned MMC servicing to get details of how the wheel is sealed. A layer of silicone is spread over the spoke area and smoothed so it resembles a rim band.
Got my trusted tyre shop to remove the tyre. Silicone layer visible as they described. Spotted a small break in the silicone matching the leaking nipple. A bit odd as to how it occured but no big deal. Advice from MMC was to reseal with silicone, let it set fully then refit the tyre. Mark the tyre/wheel to get it back on to minimise rebalancing. The silicone is black and luckily I have some to match.
So, I'll reseal with silicone and get the tyre refitted after 24 hours to allow curing of the repair. I did consider fitting a rim band as belt and braces but will just do a silicone repair first. Gomog has a section on sealing wires that shows this silicone method.
I'll take photos of the wheel for reference.

Plus Four MY23 Furka Rouge