Monday’s announcement includes a 10-year life extension for the Royal Air Force’s Eurofighter Typhoon warplanes
The two prime ministers also welcomed a package to promote clean energy worth 3.2 billion pounds
But Moscow said it was premature to reach conclusions that the flight was attacked.
He has praised the city for its efforts to create a favorable environment for foreign investors
Britain will provide 500 million pounds ($783.8 million) in credit finance for Vietnam's infrastructure development
"That indicated the enormous opportunity that there is... we believe there is much more to come."
Among agreements reached on Wednesday were a $1.4 billion, 20-year deal between Vietnam Airlines and Rolls-Royce.
Cameron will arrive in Indonesia today, before heading to Singapore, Vietnam and Malaysia.