"The main problems are that the airport environment is an alien one and processes such as check-in and security require co-operation with strict guidelines, " Ms Gough said.

BBC: Autism guide for airport travel

But now, thanks to strict regulations and international co-operation, the river is on the path to recovery.

BBC: Rhine on path to recovery

The entire operation has been conducted under strict secrecy by Cdr John du Rose, operational head of London's CID, after 18 months of investigations.

BBC: 1968: Krays held on suspicion of murder