In some cricket matches each team has only one innings of batting; follow-on in such a case is obviously inapplicable - it is found only in the longer (more traditional) two-innings-each match.
If the second team to bat scores substantially fewer runs than the first team, the first team can enforce (at their captains discretion) follow-on, instructing the second team to immediately bat again. In this case the sequence of batting innings will be first team, second team, second team and then (if needed) first team, so the second team is said to be "following on". This is in contrast to the normal progression of batting innings which is first team, second team, first team, second team.
This rules governing the circumstances in which follow-on may be enforced are found in Law 13 of the Laws of cricket.
Follow-on has two major purposes. Firstly it helps prevent unnecessary play. If the first team to bat is winning after the other side has batted, and is likely to win even after the other side has batted again, there is no need for this team to bat a second time. If the team following on does actually pass the first team score, the first team can then come back for their second innings. Either way the length of the match is usually reduced and almost always has an outcome that is not a draw.
Secondly, matches are limited (typically to five days) and if the first team is made to bat again, again scoring a high score, they may not have enough time to take 10 wickets in the final innings, resulting the match being a draw, even though one team could have scored hundreds of runs more than the other. The team batting first and winning would then face a potentially very agonizing decision in its second innings — at what point should it declare and forfeit the remainder of its innings to save precious time, to ensure it can bowl the other team out.
Because cricket pitches deteriorate as a match continues, follow on is not always enforced. This is because the team who enforced the follow on may be required to bat last, when the pitch is most difficult to bat on. If a team believes the pitch is still good (or has become good) for batting, they may elect not to enforce the follow-on, instead they will return to bat and increase their already existing lead.
The number of runs by which a team must lead to enforce follow-on upon its opponent is determined by Law 13 of the Laws of cricket, which takes the length of the match into consideration:
Where a match is shortened, the leads required to have the option of enforcing the follow-on are determined by how many days' (or part-days') play remain when the match starts. For example, suppose a match is scheduled for five days, but the first day is washed out because of rain. If the match then begins on the second scheduled day of the match, the team batting first needs a first innings lead of 150 runs or more to have the option of enforcing the follow-on. This only applies to time lost before the first ball has been bowled: if a five-day match starts on the scheduled first day but, say, the second day is completely lost, it still counts as a five-day match for the purposes of calculating the follow-on target.
Captains do not automatically choose to enforce the follow-on when they are entitled to. In two innings games, for a team batting first to win, it usually needs to dismiss the opposition twice. If it fails to do so, the game may end in a draw. So, when there is limited time available so that a team does not think it had enough time to bat again and then dismiss the opposing side, the follow-on will almost invariably be enforced. Another reason for enforcing the follow-on is the positive effect it can have on a team's morale, and the equal negative effect on that of the other.
When time is not an issue, the follow-on is often not enforced. This is partly because it is tiring for bowlers to bowl for two consecutive innings. It is also usually considered a disadvantage to bat last, when the cricket pitch had deteriorated by wear and there are more natural variations to its bounce and ability to take spin.
Mike Brearley, the captain Botham had replaced, took the reins for the third Test, at Headingley. This started out very badly: Australia scored 401 (John Dyson 102; Kim Hughes 89), and asked England to follow on after bowling them out for 174 (Lillee took 4 for 49; Lawson 3 for 32). The one bright point in the innings came from Botham, who top scored with 50 (his first since he had been made captain 13 matches earlier). In the second innings, Botham came to the crease with England on 105 for 5, still 126 behind. Matters did not improve: Geoff Boycott and Bob Taylor soon followed, and with England 135 for 7 and still 92 runs behind an innings defeat looked likely.
By all accounts, everyone on both sides thought the game was lost. Ladbrokes famously offered 500-1 against England winning the Headingley Test. (Equally famously, and controversially, two Australian players, Rod Marsh and Dennis Lillee, placed a bet on England to win, claiming that 500-1 were silly odds on any two-horse race.) When Graham Dilley joined him at the crease, Botham reportedly said, "Right then, let's have a bit of fun." Botham, with able support from the lower order, went on to make 149 not out, and gave England a slender lead of 129. The next day a fired-up Bob Willis took 8 for 43, and Australia slumped to 111 all out. It was the first time since the 1894-95 Ashes that a side following on had gone on to win a Test match.
Laxman came to the crease just before the end of Day 2, and proceeded to change the course of the match and the series. He struck for 281, at that time the record for an Indian Test batsman. He did most of his damage partnered with Rahul Dravid, who batted for 180; the two were at the crease for the entire fourth day. India progressed to 657/7 in their second innings (a lead of 383), and then on the final day had to declare the innings to make sure to have enough time to bowl Australia out, doing so shortly before lunch. By tea, Australia had scored 161/3, and a draw appeared the most likely result. Then, within minutes, Australia lost five wickets for 8 in a span of 31 balls. Harbhajan took the first two wickets in the same over, followed quickly by three wickets from Sachin Tendulkar. Australia proceeded to fell for 212 in the second innings and India won the match. Despite Harbhajan's prodigious bowling—6 for 73 to go with his seven-wicket haul from the first innings—Laxman was named man of the match. This was only the third test match (and last to date) to have been won by a side following on, as well as being the only time in history that a side has been able to declare the follow-on innings and still win. India went on to win the series, with Laxman contributing with half-centuries in both innings and Harbhajan, who was named as man of the series, taking 15 wickets in the final Test.