A combined UK and US effort has completed one of the largest property investment deals of the past couple of years. The London office of Gibson Dunn & Crutcher advised the unnamed vendor of 20 buildings, mainly in London, for £365m. The properties were acquired by a joint venture between US investor Westbrook Real Estate and private clients of property agents Jones Lang LaSalle. The purchaser was represented jointly by Nabarro Nathanson and the UK office of Jones Day Reavis & Pogue. The Nabarros team was led by partners Graham Lust and Robert Jackson. The Jones Day group included Martin Bartlam and Jeremy Davis on the finance side, Robert Gaut on tax issues and Linda Fletcher for property work. Lust said: "This is the first major deal that Nabarro Nathanson has undertaken for Westbrook. It was a complex transaction undertaken quickly. After a lengthy due diligence period, the transaction was completed within three days of the exchange of contracts. We're very happy with the outcome." The deal marks the US investors' first foray into the UK property market. A £365m transaction marks the first stage of a European investment drive. In addition to the initial three firms, Allen & Overy (A&O) and Clifford Chance were involved, acting for the banks providing acquisition finance. HypoVereinsbank put senior debt arrangements in place and was advised by A&O partners Richard De Basto and Rod Brown. Clifford Chance partners Iain Morpeth and Andrew Carnegie acted for senior and mezzanine debt provider Lehman Brothers. At one point the deal involved about 60 people advising the various parties. Outgoing lenders were represented as well. DZ Bank and Bayerische were advised by Denton Wilde Sapte. Travers Smith Braithwaite acted for Erste Bank and Herbert Smith was instructed by Norwich Union. An offshore element to the deal was handled by Jersey firms Ogier & Le Masurier, Mourant du Feu & Jeune and Olsens as well as Hassans in Gibraltar. Real estate finance partner Alan Samson led the Gibson Dunn team. He said: "It was generally a very complex transaction. It's one of the hardest I've seen for quite a while." The US firm would also have been instructed by buyer Westbrook had it not already been working with the seller. Westbrook has a longstanding relationship with Gibson Dunn, and it was former Nabarros' partner, Samson, that suggested the UK firm be used. Jones Day was duly selected by the client to work alongside Nabarros, bringing a US presence to the deal. Its involvement was primarily in the financing aspects of the transaction, leaving Nabarros to concentrate on property matters. The sale of this massive off-market portfolio comprises 20 properties with an average lot size of more than £18m. It includes central London offices, retail spaces in the South East and industrial parks in the North. Samson said that he expected his client to reinvest the proceeds of the sale during the next few months.