Technology is spurred on by war, which in turn speeds up the process of its evolution. It's fitting, in this case, that raw materials for salvage can be found in the cast-off pile of the Ministry of Defence.
Perhaps the first spur to this salvage culture was the Ministry of War's vast Disposals Sale at Great Missenden in Oxfordshire in 1946. The War Department is the MoD’s predecessor, and to recoup war debts, everything from Churchill tanks to Bailey bridges was sold. The lots covered 20 acres and the sale continued for two solid weeks.
Not only cheap vehicles and generators but also structural parts of bridges, tents and temporary structures were available; some of the Bailey bridges exist in use to this day. When WW2 ended, the Attlee government also instigated a programme to use the no-longer required corrugated iron which had been made for air-raid shelters, as prefabricated housing.
All the things scrapmen acquire were originally produced to do a job, but they were thrown out when their usefulness in that role expired. The scrapmen use a malefic alchemy by which they turn the products of the Cold War into ploughshares. The process rests upon the hunter/gatherer instincts of the skip-rakers: people who go to vehicle auctions, rake in scrapyards and dig in tips.
With dozens of shipbuilding yards, and a heavy naval presence in Scotland – vast naval bases at Scapa Flow, Invergordon and Rosyth – there was never any shortage of ship parts. That continues today, with Faslane on the west coast plus Rosyth (now run by Babcock) with its submarine graveyard.
We also have an aviation industry: with Vector at Almondbank, BAE Systems at Prestwick and Rolls-Royce at Hillington all of whose predecessors contributed to the junk pile. For example, military aircraft breakers supplied the Dakota passenger seat which Gavin Maxwell had in his cottage at Camusfearna, along with fish boxes and butter barrels fashioned into furniture.
Likewise, old and knackered road vehicles are destined for their own specialist scrapyards, such as the locally famous CWS bus breakers in Barnsley: several firms share a fifty hectare site, covered in hundreds of reduced chassis and littered with mangled wrecks, burst engine blocks and piles of impacted body parts. 
Each of these sectors – metal recyclers who break down ships, aircraft and vehicles – is controlled by SEPA. In contrast to these official operations is the approach of the inhabitants of the remote Hebridean islandsI who harvest what scrap they can and build it into their houses. Everything is used many more times than it might be elsewhere, particularly things which have had to come across at great expense on The Boat.
On South Uist, among the ruins of the black and white houses many crofts boast a caravan, either in use as additional living space or as storage overspill. Caravans are often left in situ for such long periods that blockwork walls are built around them, to protect them from the winter storms. The notionally temporary actually becomes permanent. Abandoned buses and coaches are also used for storage.
Most islanders keep their wrecked old cars, which make the inhabited areas of the island look like a low density rubbish tip. In fact, when the Atlantic began to wash away parts of the beach at Middlequarter Dunes on North Uist, the Army was enlisted to plant old cars into the ground to act as sea defences. Of course, the constant Gulfstream current also brings a constant stream of driftwood and flotsam to shore to be used for fences and firewood.
The Hebridean approach has a lot to do with the paucity of material; but expediency can also grow up around an abundant source of scrap, such as along the northern shore of Montrose Basin. As someone wrote, travellers and their elaborate mobile homes have been settled alongside the municipal tip to crop its waste: they often park up in roadside lay-bys, to set out and sort through their gleanings. 
Tourists arrive for the short summer season and also camp alongside on the older middens, from where a residue of demolished homes spews out onto the south shore, now clad in wild flowers.
Sometimes, an ideological viewpoint emerges from salvage culture. Travellers’ camps exist at Glastonbury, the New Forest, the Rhythm of Life camp in the Forest of Dean, and between 1992-4 there was a camp at Glen Shiel, which evaded not only building legislation but also anti-traveller laws. Around twenty vehicles were parked up on flat land where the old Wade road to Kyle separated from the new, skirting a disused two hundred year old bridge and the track parallel to it.
Their trucks had been narrowly saved from the breakers, the sheet alloy roofs of the caravans flapped in the wind and windows were patched with insulating tape. The vehicles were surrounded by dogs in polythene tunnel kennels, and “benders” – small yurt-like domes of plastic sheet over bent wood, with a chimney at the apex – had been erected on the grassy flood shelf of the river.
I originally wrote the passage above as part of my dissertation at architecture school, and amongst other things drew a comparison between the travellers’ benders, and the green timber diagrids then recently erected at Hooke Park College by Frei Otto, ABK and Ted Happold. Having rescued the dissertation from a 3 1/2 inch floppy disc and read through it again for the first time in years, I realised that somewhere I visited a few years after graduating actually fitted the ethos better – although not an impressive piece of contemporary architecture, more as a demonstration of an un-self-conscious way of life.
The military cast-offs, Highland canniness and New Age travellers’ sensibility merged at Balnakeil: a former RAF radar station near Cape Wrath in Sutherland. It was built in 1954 to cater for a new radar station on the nearby promontory, Faraid Head. There were barracks, mess rooms, a medical centre, canteen and so forth. But the planned ROTOR radar became obsolete before it had even been completed, so the buildings at Balnakeil lay abandoned for several years, until local artists colonised them.
Somehow, the utilitarian buildings look rather Modernist with their Crittall windows and white rendered planes; from the distant glimpse, the cluster of rooftop water tanks stand out but don't have a scale, and their tower-like silhouettes make Balnakeil seem like a Highland version of San Gimignano. There’s an interesting history of Balnakeil craft village here, and its long-serving artists have proven to be the canniest of salvage men and women, long before artisanal skip-raking and “upcycling” became fashionable among the hipsters of Shoreditch in London or the Kreuzberg in Berlin, with their tweed caps and ironic beards.
Perhaps a shift of 700 miles between the densely urban and the extremely rural makes all the difference…
