By Jess Jones Virgin Media O2 has announced the sale of a stake in its mobile towers joint venture, Cornerstone, to infrastructure investor Equitix, bagging £186m in cash. The deal, which leaves the telco with just over 25 per cent of Cornerstone after selling 8.33 per cent, involves a 16.66 per cent stake in a holding company that owns half of Cornerstone. Achal Bhuwania, chief investment officer of Equitix, called Cornerstone “the UK’s largest telecom tower portfolio” and “critical national infrastructure which is central to our mandate to invest in core infrastructure.” It comes amid an ind…