For a few days in March 2000, as the dotcom bubble neared bursting point, Cisco was the world’s most valuable company. Now the seller of networking gear is a cautionary tale, even if it is also an enduring success, with real earnings per share of four-and-a-half times what they were back then. Investors became so exuberant about the firm’s prospects 25 years ago that they valued it at more than 200 times its annual profit, or around $1trn in today’s money. Starting from a valuation that stratospheric, Cisco’s solid-but-unspectacular growth was a bitter disappointment. Its market value is now $280bn.