Some fans were left wondering why Joe Root opted not to wear a cap while hitting a century in the heat against Sri Lanka's spinners in the third one-day international.
It is not unusual to see players such as India's Virat Kohli batting with a hat on, but Root wore a helmet throughout his innings despite the humidity in Colombo.
Wearing a helmet is not compulsory for batters facing slow and medium pace bowlers in international cricket, but it is mandatory for all England players in the various formats.
The England and Wales Cricket Board's (ECB) head protection regulations were brought in to mitigate the chance of players being struck on the head by bowlers, fielders and also themselves with the bat.
The International Cricket Council (ICC) rules that batters must sport a helmet when facing pace bowlers, but it is optional at other times.
English first-class cricketers have had to wear helmets against all types of bowlers since the 2016 season, but it is not mandatory for adults at a recreational level.
Do all batters have to wear helmets?
All cricketers under the age of 18 in England and Wales must wear a head protector while batting in matches or practice sessions. Wicketkeepers under the age of 18 also have to wear a helmet when standing up to the stumps.
"The cricket ball can cause significant injury and it is extremely important that players take the appropriate precautions when batting, keeping wicket or fielding close to the stumps," said ECB chief medical officer Dr Nick Peirce when the regulations were introduced in 2015.
The ECB also advises players to wear neck protectors, but they are not mandatory. In Australia they have been compulsory for all batters facing fast or medium pace in Cricket Australia competitions since the 2023-24 season.
The regulation was brought in following the death of Phillip Hughes in 2014.
Hughes was struck on the top of the neck by a ball during a Sheffield Shield match in Sydney.
He collapsed and was taken to hospital, where he died two days later.
The neck protectors attach to helmets to provide extra protection at the back of the head and neck.
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