Alan has more than 25 years of professional experience in applying economics to aid decision-making, in particular in the regulated sectors. He specialises in efficiency measurement and assessments, regulatory reform and regulatory incentive design.

He has provided advice and expert evidence on mergers and acquisitions, regulatory due diligence, business planning, regulatory determinations, appeals and court cases. He has advised companies, investors, governments and regulatory authorities in the energy, transport, water, financial services and communications sectors across Europe.

Alan is co-author of A Practitioner’s Guide to Stochastic Frontier Analysis using Stata with S. Kumbhakar and H.-J. Wang, published by Cambridge University Press in 2015. The book provides practitioners in academia and industry with a step-by-step guide on how to conduct efficiency analysis using the econometric approach, stochastic frontier analysis.

Selected project experience

  • Advice to water companies on regulatory and efficiency issues during PR14 and PR19, including advice to Bristol Water during the CMA inquiry into its appeal of the PR14 Final Determinations (2013–18)
  • Expert testimony to the CMA for firmus energy’s price control appeal (2017)
  • Advice on how to improve efficiency for an energy client (2018)
  • Advice on regulatory framework issues in preparation for RIIO-2 controls (2017–18)
  • Advised the Netherlands Authority for Consumers and Markets on the dynamic efficiency potential for the Dutch transmission system operators (2015–17)
  • Advised BDEW, the association for all German electricity, gas and water networks, on how to set the productivity factor (2017)
  • Developed a cost forecasting framework for business planning, including an international benchmarking study, for a large international airport (2011–17)
  • Advised South West Water during the CMA inquiry into its merger with Bournemouth Water (2015)
  • Advising the boards, and legal and financial advisers, of water and energy companies on potential mergers and acquisitions, including due diligence (2001–)
  • Advice to Highways England (2014–)
  • Efficiency and incentive framework advice to the Energy Networks Association and DNOs for RIIO-ED1, including expert evidence for the CMA inquiry (2011–15)
  • A review of the efficiency regime for a German gas transmission company (2013)
  • Advice to a group of Italian water companies on developing a framework to assess cost efficiency (2013–14)
  • Advice to BT on efficiency and incentives (2011–13)
  • Advice on efficiency for an energy transmission company for RIIO-T1 (2011–13)
  • Efficiency advice to Royal Mail, including internal benchmarking (1999–2014)
  • Efficiency advice to the Finnish energy industry (2012)
  • Advice on efficiency issues for a Belgian energy distribution network (2011–12)
  • Advice on the efficiency regime for district heating in Europe (2011–12)
  • Advice to a UK gas distribution company on its Business Plan submission for the RIIO-GD1 regulatory review (2011–12)
  • Advice to a European energy regulator on alternative performance assessment approaches in electricity and gas networks (2010–12)
  • Advice on regulatory reform, including the efficiency regime, in Estonia (2010–12)
  • Advice on competition and regulatory reforms in the water industry (2010–11)
  • Examined consumption efficiency in the retail investment products market (2010)
  • Advice to major GB bus operators reviewing the likely impact of a change in the concessionary fares regime, including the efficient incremental costs (2010)
  • Advised Ofwat on various regulatory framework issues, including approaches to assessing expenditure, the menu and outcome delivery incentives (2008 and 2012)
  • Led Oxera’s efficiency advice for a number of price control reviews in energy, water, transport and communications (1996–)
  • Provided support during ten Competition Commission inquiries (1997–2012)

Selected publications

  • Kumbhakar, S., Wang, H.-J. and Horncastle, A. (2015), A Practitioners Guide to Stochastic Frontier Analysis using Stata, Cambridge University Press.
  • Arias, L. and Horncastle, A. (2011), ‘Lessons from mergers and Alliances in the British Water Industry’, chapter 3, in A. Estache (ed.), Emerging Issues in Competition, Collusion and Regulation of Network Industries, Centre for Economic Policy Research.
  • Silva Portela, M.C., Thanassoulis, E., Horncastle, A. and Maugg, T. (2011), ‘Productivity change in the Water Industry in England and Wales: Application of the Meta-Malmquist Index’, Journal of the Operational Research Society62, pp. 2173–88.
  • Kumbhakar, S. and Horncastle, A. (2010), ‘Improving the Econometric Precision of Regulatory Models’, Journal of Regulatory Economics 38:2, October, pp. 144–66.
  • Meaney, A., Horncastle, A. and Mahmood, A. (2010), ‘Efficiency, (Over-) Compensation and State Aid for PSOs’, Competition Law Journal9:3, pp. 371–8.
  • Kumbhakar, S. and Wang, H.-J., with Horncastle, A. (2010), ‘Estimation of Technical Inefficiency in Production Frontier Models Using Cross-Sectional Data’, Indian Economic Review45:2, pp. 7–77.
  • Fields, L., Horncastle, A. and Noble, R. (2009), ‘Water competition and the Cave Review: a clear way forward?’, Competition Law Journal8:3, pp. 238–47.
  • Horncastle, A., Jevons, D., Dudley, P. and Thanassoulis, E. (2006), ‘Efficiency Analysis of Delivery Offices in the Postal Sector Using Stochastic Frontier and Data Envelopment Analyses’, chapter 10, pp. 149–64, in A. Crew and P.R. Kleindorfer (eds), Liberalization of the Postal and Delivery Sector, Edward Elgar.


  • MSc Econometrics and Mathematical Economics, London School of Economics
  • BSc Economics, Analytical and Descriptive, London School of Economics