The cranes stare at each other across the City of London from the top of skyscrapers that they seem to be pulling out of the ground. On one side is British Land’s Cheesegrater, one-third pre-let, largely to U.S. insurance group Aon. On the other is Land Securities’ Walkie Talkie, a quarter pre-let to a collection of other insurers. It is not only a passion for glitzy developments that unites the two companies. They also offer very similar investment propositions, with £10-billion ($15.8-billion) portfolios focused on U.K. retail and London offices.