The term “Windrush Generation” refers to the immigrants who were invited to the UK by the British government to rebuild Britain after WWII. In 2010 the Hostile Environment policy was introduced to ensure staying in the UK was as difficult as possible for people who couldn't prove their status. Windrush individuals received letters explaining they had no right to remain in the UK, no right to medical care and lost their right to work, despite having lived there all their lives.
Burying the film symbolises the scars that Britain has put upon them, and gives them root to British society.