Mr Nathan also runs Back-Roads Touring in which FLT has a 67% stake and will continue to manage both businesses.
The deal values UK-based Topdeck Tours at £21.84m. Topdeck specialises in the “18 to 30-something” group tour market and generated sales of £43m in 2013 with pre-tax earnings of about £4m.
FLT founders Graham Turner and Geoff Lomas started Topdeck in 1973 with a 1958 old London double-decker bus.
Mr Turner ran both Topdeck and FLT, until the mid-1980s before selling out.
He bought back into Topdeck in 2003 and prior to this latest acquisition held a 4% stake.
Meanwhile, FLT today announced an underlying pre-tax profit of AUD376.5m for the 13/14 financial year, in line with forecasts.