Offshore Wind Energy has been one of the fastest-growing industries in Europe and the United Kingdom and is now gaining traction in other parts of the world too. To harvest the best winds and increase productivity, most of the new offshore projects such as the UK's Round 3 allocations will be located much farther away from the shore, which is expected to pose major problems in Operation and Maintenance (O&M). So far, research focused on the maintenance strategies for large offshore wind farms shows that the use of an Offshore Mothership is a promising option for minimizing O&M expenditure. This paper presents a design of a Mothership tailored for one of the largest offshore wind farms in the world. Special consideration has been given to the ship's layout and towards optimizing the payload to carry out a wide range of repairs.