Question: Shaun Williams plays for Millwall in which second-highest division of the English Football League?

Context articles: EFL League One
UFL Division 2
2011–12 Ipswich Town F.C. season
Colchester United F.C. league record by opponent
List of Millwall F.C. seasons
Shaun Williams (footballer)
2013–14 Ipswich Town F.C. season
2010–11 Ipswich Town F.C. season
2012–13 Ipswich Town F.C. season
2014–15 Ipswich Town F.C. season

The English Football League One (often referred to as League One for short or Sky Bet League One for sponsorship reasons) is the second-highest division of the English Football League and the third tier in the English football league system.
The United Football League Division 2, often referred to as UFL Division 2 or UFL 2, was the second-tier association football league in the Philippines.
 During its existence, it is the second-highest division of football in the Philippines after UFL Division 1.
 Each year, the winner of the league gets an automatic promotion to the latter.
 The second placer, on the other hand, goes against the ninth placer of the first division in a two-legged playoff.
The 2011–12 season was Ipswich Town's tenth consecutive season in The Football League Championship, the second-highest division in the English football league system.
 In addition to competing in The Championship, Ipswich Town also competed in the League Cup and the FA Cup.
Colchester United Football Club is an English professional football club based in Colchester, Essex, that was founded in 1937.
 From the 1937–38 season, the club played in the Southern Football League until 1950, when they were elected to the Football League.
 After playing in the Third Division South for eight seasons, Colchester remained in the Third Division when the league was re-organised by finishing 12th in 1958.
 The club were relegated to the Fourth Division in 1961, but made an immediate return to the Third Division after finishing the 1961–62 season in second position, one point behind Millwall.
 They bounced between the Third and Fourth divisions until 1990, when the club were relegated from the Football League for the first time in 40 years.
 After two seasons in the Football Conference, the U's were promoted back to the Football League after winning the Conference title on goal difference over Wycombe Wanderers in 1992.
 Colchester played in the Third Division between 1992 and 1998, when they won promotion to the Second Division after a play-off final win against Torquay United at Wembley.
 The club remained in the third tier until 2006, as they were promoted to the Championship, the second tier of English football, for the first time in their history, ending the season as runners up in League One to Southend United.
 The U's spent two seasons in the Championship, earning their highest-ever league finish of 10th position in the second tier before being relegated back to League One in 2008.
 Following relegation to League Two at the end of the 2015–16 season, Colchester made a return to the fourth tier of English football for the first time in 18-years.
This is a list of all seasons played by Millwall Football Club from their early beginnings in the Southern League, to their inaugural season in 1920–21 in the English Football League and up to their last completed season.
 It details their record in the FA Cup, the League Cup and other major competitions entered, as well as managers, top goalscorers and average home attendance for each season.
 Millwall were founded in 1885 and for the first nine years of their existence did not compete in league football.
 They first entered the FA Cup in 1887, turning full-time professional as a club in 1890.
 They were founding members of the Southern League in 1894, which they competed in for 22 seasons, claiming the title twice.
 They left to join the Football League in 1920.
 Millwall have played in all four divisions during their 91 seasons in the league, including the Third Division South, which they won twice, in 1928 and 1938.
 Millwall were Fourth Division champions in 1962.
Shaun Williams (born 19 October 1986) is an Irish professional footballer who play for League One club Millwall.
 He can play as a defensive midfielder or central defender.
 He has previously played for Drogheda United, Finn Harps, Sporting Fingal and MK Dons.
The 2013–14 season was Ipswich Town's 12th consecutive season in the Football League Championship, the second-highest division in the English football league system.
 In addition to competing in The Championship, Ipswich Town also competed in the League Cup and the FA Cup.
The 2010–11 season is Ipswich Town's ninth consecutive season in The Football League Championship, the second-highest division in the English football league system.
 In addition to competing in The Championship, Ipswich Town are also competing in the League Cup and the FA Cup.
 Manager Roy Keane was sacked after the defeat to Nottingham Forest in January after a season-and-a-half in charge.
 First-team coach Ian McParland presided over the FA Cup defeat at Chelsea and the League Cup semi-final 1st leg win over Arsenal before Paul Jewell took over the managerial role on a permanent basis.
The 2012–13 season is Ipswich Town's eleventh consecutive season in the Football League Championship, the second-highest division in the English football league system.
 In addition to competing in the Championship, Ipswich Town also competed in the League Cup and the FA Cup.
The 2014–15 season was Ipswich Town's thirteenth consecutive season in The Football League Championship, the second-highest division in the English football league system.
 In addition to competing in The Championship, Ipswich Town competed in the League Cup and the FA Cup.