Honolulu is typically 10 hours behind London. When it's 6:00 PM in London, it's 8:00 AM in Honolulu. Hawaii does not observe daylight saving time, but London does.
During UK summer time (March to October), the difference is 11 hours. During UK winter time (October to March), the difference is 10 hours.
Challenging overlap! 6:00 AM - 8:00 AM Honolulu corresponds to 4:00 PM - 6:00 PM London (winter) or 5:00 PM - 7:00 PM London (summer). Very early Honolulu catches end of London business day.
Hawaii is a popular honeymoon and vacation destination for British travelers, though the long journey requires connecting flights. The 15+ hour travel time means planning calls well in advance is essential.