| Company | Timeline | Status | |
| Johnston Engineering (Scotland) Limited Director • Director | 19 Mar 2025←7 Months→Current | Active | |
| Johnston Forensics Ltd Director • Consulting Engineer | 28 Jan 2022←2 Years 6 Months→13 Aug 2024 | Dissolved | |
| Water Engine Technologies Limited Director • Engineer | 17 Apr 2015←3 Years→4 Oct 2018 | Dissolved | |
Silver Hydro Ltd Director • Director | 24 Feb 2014←4 Years→27 Feb 2018 | Dissolved | |
Johnston Renewables Limited Director • Director | 23 May 2013←6 Years→23 Jul 2019 | Dissolved | |
Aquastars Dive Centre Limited Director • Consulting Engineer | 11 Feb 2004←15 Years→16 Jul 2019 | Dissolved | |
