A speculative bubble had been building up in London throughout the early 1890s. The dramatic reduction in external investment opportunities, with the crises in Australia, Argentina and the USA, had driven down British interest rates. This had fuelled a boom in house building and railway construction, as well as the conversion of established businesses into the joint stock form so that their shares could be sold to the public. Allied to the absence of borrowing by the British government the result was a period of low returns for investors and an increased willingness to look for new opportunities. Into this vacuum came the gold discoveries in South Africa and western Australia. Of all the metals in existence gold possessed a quality that no other had. This was its fixed price under the Gold Standard. Numerous currencies including the pound sterling had their value determined by a specific amount of gold for which they could be exchanged. Furthermore, the Bank of England was obliged to buy all gold offered to it at a fixed price. Thus, if gold could be found, mined, refined and then shipped to London it could be sold at a price known in advance. Given the discovery of new and large gold deposits in areas that were becoming accessible because of the railway, it appeared but a simple task of connecting supply and demand and profiting from the difference in price. Presented with such an opportunity investors quickly came to believe that every potential gold discovery offered a path to incalculable wealth. Gold mining appeared to possess the certainty of return that came with railways, because of their provision of a basic service, and the prospects of huge capital gain as the uncertainty of exploration gave way to the certainty of production. With gold there was no risk that the price would fall as output rose, as in the case of other metals and coal, for the demand was infinite and the price guaranteed.