He acts for a wide range of international banks, corporates and trade houses on all types of commercial litigation disputes. Andrew specialises in general commercial litigation, shipping and trading disputes. Over twenty five years, he has acted for a large number of corporates, oil majors, shipowners, insurers, charterers, operators, suppliers and cargo interests and their insurers both nationally and internationally. He has litigated in every level of Commercial Court up to the Supreme Court on two occasions (Datec –v- UPS and The Far Service). Throughout his career he has applied his skills to find commercial solutions for clients. Andrew has been rated by the directories as one of the leading shipping lawyers for many years acting for a wide range of shipowners, trading houses, charterers and their insurers. One client in the Directories said "Probably the best lawyer for head on the block advice. Andrew Preston exercises sound judgment as a gift simplifying even the most complex problems".
He steered Clyde & Co as the Global Head of Shipping for over a decade taking it to a tier 1 ranking.
Andrew is recognised as one of the leading lawyers in the world at liabilities arising out of bunker/fuel supply disputes. He was involved, together with James Kennedy, in the new Bimco bunker contracts and centrally involved in all of the major bunker events over the last years including the OW collapse, the collapse of Hanjin and the Houston problems of 2018. He is advising many industry figures in relation to 2020 issues and the forthcoming sulphur caps.
- English Electric Company –v- Alstom UK  and on appeal  (the Oliver litigation) and English Electric Company Limited –v- Alstom UK  (the Critchley litigation). These cases developed the law on liabilities and indemnities under commercial contracts for personal injury liabilities.
- FCMB –v- Zumax . This Court of Appeal decision established principles on trust relationships in banking and the extent of quistclose trusts.
- Access Bank –v- Capitol Oil . The series of linked interlocutory and final hearings established principles on freezing orders, search and seizure orders and contempt proceedings.
- Osmium Shipping Corporation –v- Cargill International SA – one of the leading cases on piracy, payments of hire following hijack and the impact of conwartime clauses on charterparty obligations.
- Enviroco Limited –v- Farstad Supply A/S – a Supreme Court case on construction of charterparty terms and obligations and defences.
- Elbourne Mitchell –v- Iron Mountain (UK) Limited – a High Court decision on the applicability of terms and conditions to warehousing contracts.
- Datec Electronic Holdings –v- UPS – House of Lords decision on applicability of package limits, the CMR Convention and wilful default.
- Mayban –v- Alstom – Commercial Court decision on cargo exclusions relating to inherent vice.