3 UK stands as a top provider of mobile phone and broadband services in both the United Kingdom and Europe. The company continues to expand its presence in international markets such as the Far East and North America. The mobile phone provider Three UK ranks as the UK's fourth-largest operator with its customer base exceeding 10 million users. Businesses have faced significant difficulties with diversity and inclusion among their employees for recent years which has particularly impacted multinational companies such as Three UK in their efforts to attract and retain staff. Some people suggest that the human resource department of these businesses might be accountable for these issues. The continued success of companies such as Three UK remains essential to producing jobs and supporting the UK's economy during the post-COVID-19 and post-Brexit period. Research shows a shortage of studies examining how HR departments promote diversity and inclusion within employee ranks. This research aimed to examine how the HR department at Three UK supports diversity and inclusion practices and its effect on business performance. The research team conducted a survey using a structured questionnaire with 100 participants who worked for Three UK. The research team implemented a content analysis technique to examine the collected data. Employee responses confirm that Three UK's HR department maintains strong inclusion and diversity standards within the workforce. Most employees reported that the company's performance likely benefited from the implementation of diversity and inclusion initiatives. The final section of this paper presents practical and policy-based implications derived from the key research findings.