The renovation of Elizabeth Tower by architecture studio Purcell, described as a "masterpiece in conservation and craftsmanship", has won a RIBA National Award.One of the UK's most recognisable buildings, the Elizabeth Tower was one of 38 projects in the UK capital recognised by Royal Institute of British Architects (RIBA) earlier this week."This project is a veritable masterclass in conservation and craftsmanship," said the jury citation."The most comprehensive programme of works in the more than 160 years since the tower was built, it represents an astonishing achievement in upgrading and preserving this monument for the benefit of future generations."Described as "probably the most iconic building in this year's RIBA Awards", the tower is home to the Big Ben bell and part of the Palace of Westminster.Purcell carried out the most extensive renovation of the tower, which was designed by Charles Barry and Augustus Pugin in the 19th century