The vacancy in Bar Cap's legal department arose after the departure of Andrew Taylor. Taylor, formerly a partner at Clifford Chance, was lured out of retirement to head Bar Cap's UK legal department at the beginning of 2001, but he parted company with Bar Cap barely a year into the post.
Taylor's responsibilities were absorbed by Alex Cameron, Bar Cap's legal director, although he was not officially promoted. Cameron is understood to be moving to a different division of Barclays.
Hughes moved into private practice after nine years at UBS and was general counsel for the Swiss bank's London operations before moving to New York in 1994. Before joining KMZ Rosenman last year he was a partner at New York's Solomon Zauderer Ellenhorn Frischer & Sharp.
Cameron declined to comment on Hughes' appointment.
Bar Cap was named as In-House Banking & Finance Team of the Year at last year's The Lawyer Awards. The team was given the award after an exceptional year that included raising $2.6bn (£1.58bn) for four Middle East schemes where it acted as lead arranger, including the $1.4m (£853,000) conventional debt for Abu Dhabi's Shuweihat power and water desalination project.