Auckland is typically 12-13 hours ahead of London, depending on the time of year. Both cities observe daylight saving time, but in opposite seasons (New Zealand's summer is UK's winter).
When both are on standard time, Auckland is 12 hours ahead. When New Zealand is on DST and UK is on standard time, it can be up to 13 hours. When UK is on DST and NZ is on standard time, it can be 11 hours.
Challenging but possible! 7:00 AM - 8:00 AM London catches 7:00 PM - 8:00 PM Auckland. Early morning London reaches evening Auckland.
Auckland and London are among the furthest apart major cities by time zones. However, strong Commonwealth ties and significant NZ diaspora in the UK mean regular communication between these distant capitals.