Veronica Castillo

Head of Production

Ronnie is responsible for all production management aspects of key new projects, particularly those with international production dimensions. She has a wealth of production expertise working as a freelance co-producer and line Producer on a number of high-profile film and TV titles over the past twenty years, including The Mark of Cain, Blind Flight, the multiple BAFTA-winning Sex Traffic, and more recently Strikeback III, Birdsong and Zen.

Billy Cook

Script Editor

Billy has a degree in Creative Writing from Bath Spa University and has been with Mammoth Screen since joining as a runner in October 2012. In his spare time he writes and dreams of things dramatic and ludicrous.

Charlotte Frings

Production & Office Co-ordinator and Executive Assistant to Jon Williams & Ronnie Castillo

Charlotte Frings started her career at the Royal Court Theatre and then became Executive Assistant to the Head of Working Title, where she assisted on productions such as Last of the Blonde Bombshells, Randall and Hopkirk (Deceased) and Ready When You Are Mr McGill.

James Gandhi

Script Editor

James joined Mammoth in May 2016 after working on the scripted comedy and drama development slates at FremantleMedia. He began his career in front of the camera, before moving to the other side to write for and develop the final two series of CBBC’s ‘Dani’s House’. He has a degree in English from Oxford University.

Chelsea Goslin-Minter

Executive Assistant

Chelsea joined Mammoth as the Office Runner in November 2014, shortly after graduating from Middlesex University with a degree in Theatre Arts. She has since progressed to the Executive Assistant to Damien Timmer, Rebecca Keane and the Executive producers. In her spare time, Chelsea loves to read and also writes her own blog.

Mark Hammond

Financial Controller

Mark joined the Mammoth Screen finance team in September 2015 as Financial Controller, adding an extra layer of support in the central finance team. Mark joins having spent the last 4 years working at ITV within the PLC finance team and more recently as financial support for the overseas production offices.


Laura Johnston

Business Affairs Manager

After studying law at Durham University, Laura was a solicitor at a leading commercial law firm before joining Mammoth in July 2016 as a Business Affairs Manager. Laura is based in the Belfast office.

Rebecca Keane

Creative Director

Rebecca has worked at Mammoth since its launch, overseeing the development slate and executive-producing various shows.

Before joining Mammoth, Rebecca was an executive producer at ITV Productions, working on a wide range of shows including Ballet Shoes, Whatever Love Means, Dracula, The History of Mr Polly, Walk Away and I Stumble, Jericho, Fallen, Daddy’s Girl, and Where the Heart Is.

Alexandra Kosevic

Production Executive

Over 20 years experience working in Production across feature films, singles and series television in the UK and abroad. Currently undertaking Ashridge’s inaugural MBA for the Creative Industries.

Preethi Mavahalli

Executive Producer

Preethi joined Mammoth in 2011. Prior to this she worked in development at Film4, and was a Development Associate on London Film School’s Hothouse programme. She has developed and produced a number of short films including a stereoscopic 3-D project and was recently appointed one of six young creative directors for the multi-disciplinary Coming Up festival created by Old Vic New Voices and IdeasTap.

Melanie Morris

Head of Business Affairs

Melanie joined Mammoth in January 2012. Previously she worked in private practice, advising a range of UK production companies, and was a production lawyer at Endemol UK and Avalon Television. Prior to this she worked in corporate law.

Tom Mullens

Executive Producer

Tom produced Black Work and Endeavour in 2014/15 for Mammoth and he’s now an executive producer across Poldark, Endeavour and Fearless.

Prior to this Tom produced a number of drama series including Waterloo Road, New Tricks and Robin Hood.

Tom started in the industry as a script editor after studying English Literature at Manchester University.

Roma Nesi Pio

Production Assistant

Roma graduated in International Relations before pursuing her passion for scripted drama and working as a floor runner for various commercial and independent production companies, among them Netflix, BBC and Somesuch Short Films.

Roma joined the Mammoth team in 2016 and, in her spare time, loves to read and go on cycling adventures.

James Penny

Commercial Director

James is primarily responsible for all Mammoth’s commercial and business affairs, having joined the company in 2012. From 2006 he was a lawyer in private practice, advising many of the UK’s leading television production companies as well as agents, broadcasters and financiers. He acted for Mammoth throughout this time, and played a leading role in the launch of the company. He is also a board member of Northern Ireland Screen.

Michael Ray

Co-Producer | Poldark

Michael joined Mammoth in August 2008, in due course rising through the ranks to his current position in the development team. He previously worked as a runner at Carnival Film & Television.

Jack Sherwood

Finance Assistant

Jack joined Mammoth Screen in September 2016 from ITV Accounts Payable department.

Jack is part AAT qualified and in his spare time he is normally found in the gym.

Joe Shrubb

Assistant Production Co-ordinator

Joe began his career in the TV industry at the BBC as a floor runner and then a 3rd Assistant Director. He left the BBC to work on various other projects, joining the crew of Mammoth Screen’s Endeavour for their third series. Joe then moved into Mammoth’s head office as the Production Assistant before progressing to Assistant Production Co-ordinator.


Paul Testar

Script Editor

Paul joined Mammoth in 2014 after graduating from Trinity College Dublin with a degree in English Literature. In his spare time he writes, produces and reviews for the theatre and has worked on several productions at the Edinburgh Fringe.

Karen Thrussell

Executive Producer

Karen joined Mammoth in 2012 after two years as Executive Producer at Chorion, looking after the film, TV and stage exploitation of literary estates for writers including Agatha Christie, Georges Simenon, Enid Blyton and Raymond Chandler.

Damien Timmer

Managing Director

Damien established Mammoth in 2007. Prior to this he was Head of Drama for ITV Productions for five years, overseeing shows including Housewife 49, Lewis, Marple. Poirot, The History of Mr Polly, Walk Away and I Stumble, Jericho, If I Had You, The Brief, London’s Burning, Me and Mrs Jones and Night and Day for ITV, and Ballet Shoes, Dracula, and Casanova (with Red Productions) for the BBC.

Himesh Velani

Assistant Management Accountant

Himesh joined Mammoth in April 2015 as an Accounts Assistant, following previously working for two years in the film industry, as a billing specialist and credit controller for Twentieth Century Fox. He is training to become a qualified accountant.

Jon Williams

Director of Production & Finance

Jon joined Mammoth Screen in 2007 and oversees all of Mammoth’s production and financial affairs. Prior to this he was Production Executive at ITV Productions, overseeing Agatha Christie’s Marple, William and Mary, The Last Detective, Whatever Love Means, Walk Away and I Stumble, The Brief, Dracula and The History of Mr Polly. 

Before this he was Finance Manager for Granada Media working on Prime Suspect, Sex Traffic, Cold Feet, Life Begins, Agatha Christie’s Poirot, Dr Zhivago, Island at War, Henry VIII and The Forsythe Saga.