This week I asked the boss of a London tech firm if a date was set for its long-touted IPO. He chuckled.  "Have you ever watched those videos of the wildebeest crossing a river with crocodiles on the attack? It's a bit like that." That is the level of trepidation tech businesses feel about the state of the London markets. There are perhaps half a dozen firms worth a billion pounds or more who would list tomorrow were conditions not so unfavourable. And frankly, they’re not getting much encouragement from the LSE’s tech incumbents, who appear to be seizing the first chance to exit. Darktrace was the latest to quit the public markets this week amid a $5.3 billion US takeover, and it moaned about the dismal share price response in London whenever its performance improved. Companies worth about £100 billion are on the way out of the London Stock Exchange so far this year, either by being bought up or via moving the main home for their shares overseas, and experts fear there is much more to come. Does that really matter? Many tech firms can comfortably pootle along privately with the support of venture capital and specialist investors....