He was interested in lichen from his teens, and developed his interests in lichen ecology and taxonomy as well as the specimen curation and identification required by his post. This included curating the collection of specimens from Erik Acharius held at the Museum. He helped establish the use of chemotaxonomy for lichens at the Museum and was active in verifying specimens sent to the Museum. His application of the International Code of Botanical Nomenclature was sometimes controversial and led to changes in the code so that species names could be proposed for retention. He published over 150 articles and several books during his career. These included a popular book Lichens illustrated with his own photographs. In 1956 he published a survey of the lichens of Northamptonshire, and was the first to apply the Scandinavian method of lichen communities to the UK. In 1960 his observation of Lecideaoligotropha in Northamptonshire was published. His surveys of the lichens of London in the late 1960s were the first to map species distributions relative to atmospheric sulphur dioxide levels. His records from gravestones demonstrated that lichen communities were retained on old memorials but did not colonise new ones. He continued to record and publish about lichen distributions until 2012, showing that lichens returned once sulphur dioxide levels fell. Laundon was a founder member of the . He was President of the society in 1984–1985, having been editor of the British Lichen Society Bulletin from 1963 until 1979, and Honorary Secretary from 1964 - 1984. He was elected as Honorary member of the Society in 1988, and received the Ursula Duncan Award in recognition of his services to the British Lichen Society in 2007. He edited ' from 1971 until 1979 and the ' from 1977 until 1990. He was a life member of the , and was awarded a Fellowship of the Association in 1972. He was required to retire in 1990 as part of restructuring at the Museum as it moved away from taxonomy, but he continued to be very active with lichens and Northamptonshire local history, including authoring several publication, until mid-December 2016, shortly before his death.
Legacy
The lichen Lepraria jackii was named in his honour in 1992, and the chemicals jackinic acid and norjackinic acid were described in 1995 and named after him. Trees were planted in his memory by the Kettering and District Natural History Society at in November 2019
Selected publications
The most significant among his 150 publications were: Laundon, J. R. Lichenologist42 6 631-636 Laundon, J. R. Lichenologist40 5 411-414 Laundon, J. R. Botanical Journal of the Linnean Society147 4 483-499 Laundon, J. R. Six lichens of the Lecanora varia group. Nova Hedwiga76 1-2 83-111 Roos, M and Laundon, J. R. On the Classification of lichen photomorphs. Taxon44 3 387-389 Elix, J.A., Naidu, R. and Laundon, J. R. The structure and synthesis of 4-oxypannaric acid 2-methyl ester, a dibenzofuran from the lichen Leproloma diffusum. Australian Journal of Chemistry47 4 703-714 Laundon, J. R. Lichenologist24 4 315-350 Diamantopoulos, I., Pirintsos, S., Laundon, J.R. and Vokou, D. Lichenologist24 1 63-71 Laundon, J. R. Lichenologist21 1 1-22 Laundon, J. R. Lichenologist16 3 211-239 Jones, D., Wilson, M.J. and Laundon, J. R. . Lichenologist14 3 281-286 Laundon, J. R. Lichenologist13 2 101-121 Laundon, J. R. . Lichenologist11 1 1-26 Laundon, J. R. Lichenologist10 2 221-225
