Saudia Airlines: SIN -> LHR $319 (May/June/July 2013 Certain Dates Only)
This was posted 4 months 16 days ago, and might be an out-dated deal
Amazing price for a trip from Singapore to London.
Only certain dates are available at the price of $319, couple this with a cheap fair with scoot or similar (~$200 or less) from Syd/GC etc and you're looking at a one way trip to London for $500 or less.
Dates which I found that are working are May 8th, 11th and the 18th. Some dates in June and July are showing up which is great considering mid year is usually pretty damn expensive.