Nuttalls are defined as peaks in England and Wales above 2,000 feet (609.6 m) in height, the general requirement to be called a "mountain" in the British Isles, and with a prominence above 15 metres (49 ft 3 in); a mix of imperial and metric thresholds.

[8] In response, Alan Dawson introduced the Hewitts, with a higher prominence threshold of 30 metres (98 ft 5 in).

[11] However, both the Nuttall and Hewitt classifications have become popular with peak baggers, and both remain in use, and their respective authors maintain up to date lists, as does the Database of British and Irish Hills.

[12] A register of people who declare they have climbed all of the Nuttalls is kept by the Long Distance Walkers Association ("LDWA"); As of October 2018[update], it totalled 302 names.

The DoBIH uses the following codes for the various classifications of mountains and hills in the British Isles, which many of the above peaks also fall into:[20][21] suffixes: = twin *on the boundary between two or three (**) parishes