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A tube driver who suffers from a form of colour blindness is believed to be the first in the world with the condition to be allowed to drive a subway train.

Alex Bulley, 26, has been permitted to work on the Jubilee line because it no longer has red and green signals and uses automatic trains that “drive themselves”.

He is the first of four candidates with “colour vision deficiency” to be approved for driving after Transport for London began reviewing its vision standards to take account of advances in technology on the Underground.

Mr Bulley, from Stanmore, was formally appointed last month after driving under supervision for a year.

He first discovered he struggled to differentiate between shades of red and green after applying for promotion to a Tube driver in 2016. He had started work as a customer services assistant at Camden Town station but wanted to achieve his “dream” of being a driver.

A customer services assistant earns from £26,000 a year but a driver’s salary starts at £33,600 and increases to £55,000.

He failed the “Ishihara” test, which requires candidates to view images formed from red and green dots.

“I was told I was colour vision deficient, which was news to me,” Mr Bulley told the Standard.

His elder brother Adrian, who was already a Tube driver, asked Joe Brown, the Jubilee line’s train operations manager, to help.

Mr Brown undertook a comprehensive review of safety risks in allowing people with colour-affected vision to drive trains.

This included making changes to Tube practices, such as platform staff using coloured light signals to dispatch trains.

Mr Bulley began driving under supervision in February last year and passed the year-long assessment without errors.

Three others with a similar problem are being assessed.

Two are experienced drivers discovered to have a red-green colour deficiency. The fourth is the son of a driver who wanted to become a driver himself.

The Jubilee is one of four automatic Tube lines with computers controlling acceleration and braking.

The others are the Northern, Victoria and Central, and automation is being introduced on sub-surface lines.

Mr Brown said: “Traditional red and green signals are going to be consigned to history at some point.”