Arsenal edged closer to the Champions League knockout stages as Bukayo Saka's goal and assist helped them to a commanding 2-0 win over Group B opponents Sevilla at the Emirates Stadium.
With London placed in Tier 2 following the end of the national lockdown on 2 December, the Hammers became the first side to welcome back fans in the Premier League after a nine-month absence.
Pep Guardiola's side, taking part in the tournament after winning last season's Champions League, made the ideal start as Alvarez struck after 40 seconds, chesting in from close range after Nathan Ake's long-range strike hit the post.