Cells were extracted from tissue as follows: Each tissue sample was washed successively in 10% w/w iodinated povidone (0.025g/10mL, Ecolab, #3030440), 70% ethanol (Sigma Aldrich, #32221) and twice in 0.05mg/mL gentamycin solution (Sigma Aldrich, #G1397), before being floated dermis side down in 10mg/mL dispase II solution (Gibco, #17105041) overnight at 4C. The epidermis was peeled and disposed of. The remaining dermis was dissociated using a Human Whole Skin Dissociation kit (Miltenyi Biotec, #130-101-540) as per manufacturer's instructions. The resulting cell suspension (passage-zero) was frozen at -80C in complete media with 40% FBS and 10% DMSO (Sigma Aldrich, #D2650) before being moved to vapour-phase nitrogen for long term storage. Cells were thawed immediately prior to processing for sequencing.  To gain passage-4 cells, an aliquot of passage-zero cells were thawed and cultured in 2D adherent cultures in complete media (high-glucose Dulbecco's Modified Eagle Medium (DMEM) with GlutaMAX and pyruvate (Gibco, #31966021) supplemented with 10% fetal bovine serum (FBS; Cytiva, #SV30160.03) and 1% penicillin/streptomycin (Sigma-Aldrich, #P0781) until 80% confluent. Cells were detached each subpassage by incubation with trypsin-EDTA solution (Sigma-Aldrich, #T4174) for 5 mins at 37C. Cells were subsequently replated and allowed to further culture until the 4th passage, at which point the cells were subpassaged and collected as a single cell suspension.  All cell suspensions were purified for live cells using MACS Dead Cell removal kit (130-090-101) immediately prior to processing for sequencing. Library preparation (Chromium 10X  single cell 3' version 3)  proceeded following manufacturer's instructions and was carried out by specialists in the King's Genomics Centre  (Waterloo) at King's College London. Sequencing was performed on an Illumina HiSeq system.