I think this basically asks you to answer the usual 'Why you?' 'Why commercial law?' 'Why the firm?' questions. However, given the short word count limit and the framing of the question in terms of explaining "who you are", I agree with
@Tintin06 that you should try to showcase a narrative. Thus, instead of separating your answer between three distinct paragraphs addressing each issue, you may want to focus on the series of experiences that led you to where you are today. This way, when discussing each experience you can also discuss the commercial law,
Freshfields and 'why me' connections.