London weighting is an allowance paid to certain civil servants, teachers, airline employees, PhD students, police and security officers in and around London, the capital of the United Kingdom. It is designed to help these workers with the cost of living in Greater London, which is higher than that of the rest of the UK. Its purpose is to encourage key workers to stay in Greater London. - https://en.wikipedia.org/wiki/London_weighting

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The University recognises that there may be exceptional circumstances when, for particular groups of roles in certain disciplines, recruitment and/or retention levels cannot be maintained to meet the needs of the University because such roles or disciplines may attract higher salaries externally. In such circumstances a Market Weighting Allowance may be paid in addition to base salary at the appropriate grade (as evaluated through the HAY job evaluation scheme) to bring total pay in line with pay in other organisations.

Market Weighting Allowances will only be appropriate where particular roles have been identified as requiring a market premium; the weighting applies to all of those roles as a group. Market Weighting Allowances are variable pay elements which are subject to change; they will therefore be paid as a separate allowance on a monthly basis and are non-pensionable.

Market Weighting Allowances are applicable to job particular families/groups of roles, and not to individual employees, and so should not be used to secure the recruitment or retention of individual ‘talent’; Consideration should be given to the Personal Value Allowance policy in such cases.

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Salaries reflect the full range of duties within the role including any requirement for out of hours working and include a £1,200 per annum local market weighting factor encompassed to cover this. - http://watford.moderngov.co.uk/documents/g1014/Public report...