In the UK, the earliest work on listing mountains was done by Sir Hugh Munro in 1891. He required a significant mountain to have a summit height of at least 3000 ft and 'sufficient separation' from other summits. However, he never defined what 'sufficient separation' meant and his classification (modified by others numerous times) contains topographical inconsistencies together with a few very dull peaks.
Later developers of hill lists, starting with John Rooke Corbett in the 1920s, not only gave a height criterion (in Corbett’s case a summit height of 2 500-3 000 ft) but also required a "drop" or prominence of 500 ft to a higher summit. Walkers have often noted that Corbett’s list generally consists of interesting peaks.
There is good reason to think that combining suitable height and prominence criteria is necessary to have a challenging list of peaks. Consider the following example, which uses height and prominence sizes that are appropriate for the UK.
All three peaks in the illustration have a prominence of 500 metres, yet they have summit heights of 600, 850 and 1100 metres. The 600 m summit on the right would require the walker to start at close to sea level. The 850-metre summit is higher but if the walker started walking from a valley with elevation 350 metres, the challenge would be no greater than for the 600 metre summit. Similarly, if a walker starts to ascend the 1100 m summit on the left from a plateau at 600 m, the challenge is equal to that of the other peaks.
Conversely consider three summits all of height 1 000 metres but with differing prominence.
The summit on the left with prominence 100 m would be an interesting peak on a mountainous ridge but would be unlikely to be considered a significant mountain in its own right. The middle peak with prominence of 200 m would be generally considered a more interesting challenge. However, the peak on the right with a prominence of 500 m will be either a distinct peak or the dominant peak of a mountainous ridge.
Therefore a meaningful classification of peaks should include both height and prominence criteria. A demanding prominence criterion is likely to result in a challenging list of hills. If a weak prominence criterion is used to define a list, (e.g. less than 100 m in the UK), it risks including some less rewarding summits.
The conclusion of the authors is that there is a strong case for classifying peaks by height and prominence. The UK Prominent Peaks database on this website is based on demanding at least 500 metres in height and at least 100 metres in prominence. The Bloomer's Challenge is based on the demanding prominence criterion of 500 metres.