Kolpak

A 2003 European Union ruling on the right of a Slovakian handball player to play in Germany has had a massive impact on English county cricket. It created an opening for players from countries with trade agreements with the EU (in effect South Africa, Zimbabwe and some Caribbean countries) to bypass the limits on overseas players and sign for counties. A trickle became a flood, and by 2008 there were more than 60 Kolpak cricketers in England, causing debate and acrimony between counties with arguments that their presence weakened English cricket. Click here for a more in-depth explanation.

Jan 9, 2017: Kolpak-alypse now? | Jan 9, 2017: Wiese joins Sussex on three-year Kolpak deal

Ball-tampering

Players are barred, by Law 42.3, from rubbing the ball on the ground, interfering with its seam or surface, or using any implement that can alter the condition of the ball to thereby gain unfair advantage. There have been plenty of ugly incidents centring on accusations of ball-tampering through cricket's history: the John Lever "Vaseline" affair in 1976-77; the times England and New Zealand accused Pakistan of it in the early 1990s; Michael Atherton's admission that he used dirt to treat the ball against South Africa in 1994; and perhaps most infamously, the Oval Test of 2006 when Pakistan forfeited the match because they were accused of having tampered with the ball.

Jan 2, 2017: Margins, morality, and the many collapses of 2016 | Nov 22, 2016: Too much being made of du Plessis episode - Gillespie

Australian cricket under review

Australia lost more than a Test series when the Ashes were surrendered to England in January 2011. The overall health of Australian cricket was called into serious question by an unprecedented three innings defeats in five Test matches, leading to a review of the national team. Also up for debate was the state of cricket's administration, as the Cricket Australia board maintained an archaic structure with 19th-century origins.

Dec 20, 2016: How CA and the players' association are drifting antagonistically apart | Jun 25, 2013: Arthur accepts axe decision

The Pakistan spot-fixing case

In September 2010 the ICC suspended three Pakistan players - Mohammad Amir, Mohammad Asif and Salman Butt - on allegations of what was later defined as spot-fixing. They were alleged to have carried out specific on-field actions, including bowling no-balls at pre-determined times, during the Lord's Test against England on the instance of a bookie. The three were later handed long bans by the ICC before the matter moved to the British Crown courts, where all three were convicted and sentenced to spells of detention.

Jun 20, 2016: 'The dream is to come back and play for three to four years' | Aug 19, 2015: Bazid: Trio's return would be unfair to the rest

New Zealand's captaincy controversy

Ross Taylor led New Zealand to their first Test victory over Sri Lanka in over a dozen years in December 2012, but he then stepped down from the captaincy, opted out of the tour of South Africa, and Brendon McCullum was appointed his successor. Taylor countered claims by New Zealand Cricket that he had refused to accept a two-way split of the captaincy with McCullum, and said the coach, Mike Hesson, had questioned his leadership and said he would ask the board to replace him.

Jun 15, 2016: 'The captaincy came a couple of years before I was ready' | Oct 24, 2016: Taylor did not communicate with his team - Brendon McCullum

Sledging

From WG Grace, with his penchant for delivering a running commentary on opposition players and umpires, to Steve Waugh's Australians and their tactic of "mental disintegration", sledging is almost as old as cricket itself. The Australians, from Dennis Lillee to Merv Hughes have been the acknowledged masters, but Asian exponents like Kumar Sangakkara are fast catching up

Mar 21, 2016: Does sledging drive people away from the recreational game? | Nov 2016: Winter is here

Cricket rules

Cricket has never stopped evolving: from round-arm bowling becoming the standard, to the 15-degree rule for arm flexion while bowling. From the number of balls per over to the specifications of equipment - ranging from glove-webbing to bat handles - almost every aspect of the game is regulated. New rules are frequently put in place - especially in the shorter forms of the game, as in the case of Powerplays, free hits, and the tweaking of field restrictions.

Feb 21, 2016: Bring back the back-foot no-ball law | Sep 30, 2015: MCC revises fielder movement Law