Herbert Smith Freehills (HSF) and Ashurst have picked up the lead legal roles on O2 parent company Telefonica's plans for an initial public offering (IPO) of the UK telecoms company.

If the float goes ahead, it looks set to be one of the largest London IPOs since Glencore's $10bn offering in 2011. The size of the stake Telefonica plans to list is not yet clear, although a figure of 30% has been reported.