Former cabinet minister Byrne and ex-John Lewis chief Street now go through to a second round run-off, with a final result expected late on Saturday afternoon.
Victory for Labour would mark a significant consolation for Sir Keir Starmer, denying Boris Johnson a hat-trick in the three most prominent “super Thursday” election tussles in England, after emphatic Tory triumphs in the Hartlepool by-election and contest for Tees Valley mayor.
Polling ahead of the West Midlands contest suggested that Mr Street was set to extend the wafer-thin majority he secured in 2017, when he saw off Labour’s Sion Simon by 50.4 to 49.6 per cent in the second round.
Mr Byrne, the MP for Birmingham Hodge Hill who served in Gordon Brown’s cabinet from 2008-10 and famously left a note in the Treasury to tell his successor there was “no money”, now needs to pick up only around 5,000 second-preference votes to win the West Midlands mayoralty.
Labour aides were hopeful of securing that number from the 12,435 who voted Green and 9,294 who backed Liberal Democrats in the first round, with a further 3,496 voting for Reform UK.