In a comment on one of my cricket posts, Jackie asked:

would u please explain the “follow on rule” how it worked out?

The follow-on rule (Law 13) is an interesting piece of tactical complexity. It only applies to two-innings-a-side games. Basically if, at the end of the first innings each, the side batting first has a huge lead, it can require the side batting second to bat again immediately. So instead of the order of innings being A-B-A-B, it will be A-B-B-A, with A only having to bat again if they need to.

What does a “huge lead” mean? Well, it depends on the length of the game. The current rules are:

200 runs in a match of 5 or more days;
150 runs in a match of 3 or 4 days;
100 runs in a 2-day match;
75 runs in a 1-day match.

The rule came into play in the current test match between England and South Africa, so I’ll use that as an example. England batted first and made 593 (for 8 wickets, declared). In their first innings South Africa were all out for 247. That gave England a lead of 346 – substantially more than the 200 required to bring the follow-on rule into play. So England had the right to ask South Africa to bat again. Michael Vaughan chose to exercise the option, and so South Africa are batting as I type.

As with much of cricket, the interest comes in the application of the tactics. There was much discussion amongst the commentators as to whether Vaughan should ask South Africa to bat again. He didn’t have to, and there are good reasons why he might not do so. Firstly his team only has four specialist bowlers, and it might have been better to give them a day of rest. Additionally England’s most effective bowler had been Panesar, and spinners are always most effective late on in the game when the pitch has been roughed up by being walked on for several days.

On the other hand, the South African batsmen were probably demoralized and putting them back in straight away would have kept them under pressure. There is also the threat of rain to worry about. The sooner England can wrap up the game the better. And the timing was fortuitous. There is nothing that opening batsmen dislike more than having to bat for just a few overs at the end of the day, and Graeme Smith very nearly got out off the last ball of the day. Vaughan might also have judged that the South African spinner, Harris, was not very good, and therefore would not be a great threat if England did have to bat on day 5.

Many people complain that the longer forms of cricket are boring, but these sorts of tactical considerations only become meaningful in longer games. Test cricket is often described as being like a chess match, and it is rules like the follow-on that help make it so.