Who is she?
Gloag and her brother Brian Souter (together now worth £159 million) founded public transport concern Stagecoach in 1980.
How did she make her millions?
They took over small city bus firms and priced rivals out of the market.
In the '90s, they bought Sweden's Swebus for £233 million (sold in 2000, with a £103.5 million debt, for £100 million) and South West Trains for £1. Stagecoach floated in '93, joining the FTSE 100 in '98. It's now worth £1.1 billion.
What's the secret to her success?
Legendarily hard-nosed, Gloag is feared for her negotiating skills. The Competition Commission once called her firm's methods 'predatory, deplorable and against the public interest'.