YeoPhotoGroup by Keith Robins

World's smallest, simplest and cheapest flashgun!
Remember the old fashioned Magicube flashes that sat on top of a Kodak 110 mini instamatic camera? They were surprisingly powerful, equal to a Sunpak GT32.
Inside a Magicube is a tube full of oxygen which when tapped by the internal spring would shoot up and mix with the zirconium foil in the glass orb and instantly give off a really bright light. 180 degree spread of light lasting about 1/30th of a second, just right for illuminating a waterfall but without freezing the moving water, brilliant! With a guide number of 80 in feet at 50ASA, because that's what 200 comes down to when underground, this was one of the most powerful guns available without going overboard with the costs. Remember, this was the late seventies and almost everyone was on the breadline.
The little alloy plate and galvanised sheet tin holder / trigger cost less than fifty pence and took me only an hour each to make. All three of us in the AVRG cave photography group had one or two and is what most of the caving pushbike was lit with.
This was back in 1978-82 when over a four year period I went caving 400 times and took one roll of film each trip. I can hardly believe that I ended up with 15,000 slides on Ektachrome 200. Being a self develope film the costs were kept to a minimum at £19 per hundred foot roll, enough for twenty times thirtysix exposures. Add on the tiny expense of a developing kit, plus hours of fun chattering and twiddling the films in their tanks, sometime three at a time with the chemicals being poured from one tank to another. We talked photo and took photos and there was little time for anything else, but then, what other hobby is so versatile in the areas into which you can lose yourselves for hours on end?
Obviously there was great excitement as super picture like these were revealed after fifty minutes of twiddling. God, it's fantastic that nowadays we can download five times that number and see the results straight away and print them off before an old slide film was anywhere near dry.
The hieght of our cave photography was taking a pushbike down Swildon's Hole on the Mendips. This was to be for an audio visual to show at the Bristol University caving conference. Once word got out the main lecture theatre was bursting at the seams with almost double the fire safety recommended numbers crammed into every corner, even sat on the stairs because they'd heard of the content. What!? Took a pushbike down through Swildon's!!! Definitely our happiest hour!
I'll be trying my best to put this AV on the net and let you have the link as soon as I can.