Paul C

Are you saying that the iPhone, when connected to the same wifi network as (for example) a laptop computer, gives much worse speed test results? It would seem odd, but maybe an explanation is that some networks throttle or disallow speed tests (it is quite network-heavy), maybe with their "network traffic rule" coming into play after say 500mb or so of data is through - so it could make sense that a 2nd, 3rd etc test is much slower than the first. If its mobile network, not wifi, then was the iPhone inside the boat? I have noticed sometimes the "faraday cage" effect absolutely hammers a mobile phone's performance, while other times its completely unaffected - I can only assume this is due to the frequencies used. Having it by a window can help too.

As an update, we're out and about again on the canals. I'm not going to do thorough testing at each location this time, but I have 3 devices to connect to the internet: O2 (Giffgaff) mifi router with external aerial; 2nd mifi router with external aerial (Lyca mobile cheap SIM, EE network but not band 20); iPhone with Talk-home SIM (EE network, not sure on band 20) .................................................................Giffgaff mifi......................Lyca mifi...................Talk-home (iPhone) Just above Audlem 15....................22Mbps..............................4Mbps.......................10Mbps near Market Drayton.......................5Mbps................................22Mbps.....................115Mbps (5G connection) So it goes to show, that no one network is "the best" in all areas. And that the cheap mifi units seem to have an upper limit for speed, which is no doubt due to the technology used, eg MIMO, Cat. I am sure a more expensive mifi would be able to achieve/exceed the speeds of the iPhone.

https://www.smlmarinepaints.co.uk/uploads/files/library/files/DATA_SHEETS/Jotamastic_90_AG.pdf

Why do people get so confused at staircase locks? Water fairly consistently flows downhill.....