Abstract: This invention relates to sealing compositions and, more particularly, sealing compositions for use in conjunction with tail seals of tunnelling machines. In particular a sealing composition according to the invention comprises, by mass, from 10 to 55% of a petroleum-derived wax, or wax-consistency hydrogenated vegetable oil or fat, or a polyisoobutane of oil, grease or wax consistency, or any combination of the above, from 0.5 to 15% of a lipophilic emulsifier, and water in sufficient concentration (at least 20% preferably 20-75%) to inhibit combustion of the composition.