Having been a member of the Essex Academy since the age of 16, Cook was given his first-class debut for Essex against Nottinghamshire County Cricket Club on leaving school at the end of the 2003 season; put in to field he aided the first dismissal with a catch before scoring just 13 runs in his first innings but pushing Essex to a nine wicket victory with 69 not out in the second.
Despite Essex's relegation being assured, Cook still battled away with an opening stand of 122 opposite Will Jefferson in the second innings of his second match, against Warwickshire.
In the six innings in which he participated he quickly racked up three half centuries at an average of 47.80.
Having secured his place as opener in the county team, he made his maiden first-class century against Leicestershire in May 2004 with 126 opposite Jefferson's 128 for a 265 opening stand, Essex's third highest but the team failed to secure promotion.

His exploits in his single season gained enough attention for him to be brought in as opening batsman for the MCC in 2005 season's opener against County Champions Warwickshire.
With a century in the first innings and 97 in the second, Cook helped secure victory in a match destined for a draw.
The season opener would not be Cook's only highlight for the year: as the Ashes approached, Australia were touring the counties and in a two-day match (which did not count towards his first-class statistics) Cook scored a double century and went on to take the first wicket of Justin Langer with a catch in the drawn match days after being awarded PCA Young Cricketer of the Year.
A further highlight of the season saw Cook help Essex to achieve one of Durham's two defeats of the season, scoring 107 of Essex's 245 before taking his maiden first-class wicket, followed by another two, with his off-spin.
Cook played in every first-class match for Essex and also helped them clinch the Totesport League Title for the first time in 20 years.
The end of the season saw Cook finish with an average of 48.03 in the County Championship, hitting four centuries.
Having been a member of the Essex Academy since the age of 16, Cook was given his first-class debut for Essex against Nottinghamshire County Cricket Club on leaving school at the end of the 2003 season; put in to field he aided the first dismissal with a catch before scoring just 13 runs in his first innings but pushing Essex to a nine wicket victory with 69 not out in the second. Despite Essex's relegation being assured, Cook still battled away with an opening stand of 122 opposite Will Jefferson in the second innings of his second match, against Warwickshire. In the six innings in which he participated he quickly racked up three half centuries at an average of 47.80. Having secured his place as opener in the county team, he made his maiden first-class century against Leicestershire in May 2004 with 126 opposite Jefferson's 128 for a 265 opening stand, Essex's third highest but the team failed to secure promotion.
His exploits in his single season gained enough attention for him to be brought in as opening batsman for the MCC in 2005 season's opener against County Champions Warwickshire. With a century in the first innings and 97 in the second, Cook helped secure victory in a match destined for a draw. The season opener would not be Cook's only highlight for the year: as the Ashes approached, Australia were touring the counties and in a two-day match (which did not count towards his first-class statistics) Cook scored a double century and went on to take the first wicket of Justin Langer with a catch in the drawn match days after being awarded PCA Young Cricketer of the Year. A further highlight of the season saw Cook help Essex to achieve one of Durham's two defeats of the season, scoring 107 of Essex's 245 before taking his maiden first-class wicket, followed by another two, with his off-spin. Cook played in every first-class match for Essex and also helped them clinch the Totesport League Title for the first time in 20 years. The end of the season saw Cook finish with an average of 48.03 in the County Championship, hitting four centuries.
Alastair Cook