LONDON, Dec 21 (Reuters) - Total shopper numbers across British retail destinations rose 2.3% in the week to Dec. 19 compared to the previous week, reflecting Christmas demand, market researcher Springboard said on Monday. It said shopper numbers, or footfall, rose by 6.2% in shopping centres and by 4.9% in retail parks, but declined in high streets across the UK by 0.8%. Springboard said the introduction of more severe Tier 4 restrictions to try to curb a new faster spreading strain of COVID-19 meant footfall on Dec. 20 slumped 39.9% versus the previous Sunday. The new restrictions forced all shops deemed “non-essential” in Tier 4 areas to close. (Reporting by James Davey; Editing by Kate Holton)