By Rupert Hargreaves The London-listed real estate investment trust Assura and the Universities Superannuation Scheme Limited (USS) have agreed to invest £250m in a 20:80 joint venture to support investment in essential NHS infrastructure. In an announcement published this morning, Assura, the UK’s leading specialist healthcare property investor and developer, said it would take the 20 per cent stake and “act as property and asset manager, receiving asset management fees linked to the valuation of the portfolio.” The real estate investment trust added that it would work with the £75bn USS pens…