Not a cave plaque for one individual, but a group of individuals: Chartist Cave - http://www.ogof.org.uk/chartists-cave.html
Here's a link to an image of the Mossdale Caverns plaque: https://www.grough.co.uk/magazine/2017/06/23/service-marks-50th-anniversary-of-mossdale-caverns-tragedy-cavings-worst-disaster
There's a plaque to Roger Solari on the approach to Terminal Sump (Sump 1) in Agen Allwedd. He lost his life in Sump 4 in June 1974 (and his remains are still there). In late March/April 1974 the cleaning lady for my floor in the Rootes Hall of Residences at the University of Warwick, who was psychic and would do the Tarot for you if you asked, told me that she had just seen the 'sign of the coffin' in my sheets, whilst making my bed . . . She said that a death was going to occur that would be significant to me, but it did not mean trouble with my forthcoming exams! Well, absolutely no one in my family or any friends I knew at the time died and so it all seemed to be a false alarm. Yet I later, after graduating, ended up editing a sailing film for BBC TV in which Michael Bentine took part. He was absolutely certain that there is more to this world than we are fully aware of and spent much time researching 'the power of the human mind', as he subsequently described to me when we were planning a series on unexplained phenomenon that he was going to present and Bruce Bedford (founder and first editor of Descent
magazine) was to have written - called Mapping the Mysteries
. But, Channel 4 commissioning editors were a nightmare to get anywhere with and Michael died before we could get started. But, as my involvement with the exploration of the Llangattock caves started to take off (I and Rob Parker, who I met as a result, carried diving equipment for Martyn Farr's and Rob Palmer's first dive back into Maytime in Agen Allwedd in 1981 since the 1974 incident) the significance of the date when Roger Solari died finally started to sink in. So, when the opportunity came on the Friday night to push the first Daren Cilau breakthrough in 21 years through an open hole that I'd just opened up that night, I persuaded Jock Williams that we should wait for Martyn Farr and the others who were going to come in with us the following day. And after Martyn separated from his first wife, Sally, and consequently disappeared for a while from the pushing scene in Daren, it's a significant part of why I contacted him a second time out of the blue to join in for the Welly Boy Aven trip (see below). As a result Martyn ultimately ended up completing the dive through the mountain that he'd been unable to do with Roger in 1974. Martyn exited the dive via Elm Hole - which had first been dived in the 1970s by Roger Solari and where jock Williams and I helped him to recommence diving into the mountain in 1986 (there's a picture of the three of us together in wetsuits in the Clydach Gorge on the day) . . . and I still don't know the ultimate 'meaning' of all this.
I don't know if it is still there, but there was a plaque attached to a large boulder just prior to the entrance of Eglwys Faen cave in the Craig y Cilau NNR at Llangattock, Crickhowell, South Wales, in memory of Bill Gascoine. Bill was secretary of the local cave management group for a good many years and carried out a number of significant first long-distance dye traces underground, linking various surface sinks and underground sites with resurgences in the area and South Wales in general. There doesn't appear to be a picture available online, although I have a copy of an image of the plaque taken shortly after it was placed (with permission) by local cavers.
In the case of Giles Barker, it is good to see he has a memorial in Spain and that the local people have wanted to honour his memory. I was sitting on a London Underground Northern Line train about to pull into Bank or the next station or so heading north when, in the days of having to pay 50p for the newspaper, I saw a spare copy of the Evening Standard
lying on the seat facing me. I just had time to read the short 'Stop Press' items on the back page, which used to give up-to-the-minute news in the days when most news was hours old by the time it reached the printing presses. In fact, I ended up reading only one item. It was headlined: 'Caver Killed in Northern Spain' . . . I then saw the name 'Giles Barker' at the bottom. All of a sudden the train stopped at the station where I had to get off and the doors opened. Not knowing which way to turn, I quickly tore the relevant piece out of the paper before hurriedly exiting the carriage - just in time prior to the doors closing and the train departing - leaving me standing on the platform, stunned.
Giles lent me the two ropes that were used to simultaneously climb the end of Preliminary Passage (Steve Holmes and Adrian Hanson-Abbott) and Welly Boy Aven (Tony White, Martyn Farr and Dick Gledhill) in Daren Cilau in February 1985. After Steve's best lead panned out at a horrible perched boulder choke, Dick came back to acquire the two ladders and second rope we had, which ended up being used by Tony (who'd successfully scaled the second-best lead to discover Higher Things) to make the first descent into White Passage. This is a memorial to Giles which will always be there, so long as the cave continues to exist - yet the plaque erected in Spain is, also, much appreciated.
There are plenty of people who seem to want to begrudge much in the world, especially when it comes to acknowledging others who are not themselves. I think the fewer the number of plaques the better, but, where appropriate, a plaque well placed can honour the memory of someone who has played a significant part in life or made a sacrifice locally. I can't think of a better example than the plaque at Grotte de la Luire in the Vercors, France, which I descended with Rob Murgatroyd in 1990, thanks to a welcoming, joint French-Italian summer-expedition scientific exploration of the cave, to a deep dry 'sump' from which I have a couple of rounded pebbles: https://baladesenisere.wordpress.com/2014/09/15/grotte-de-la-luire/
(penultimate image on the page).