It is 12 months since the body of Jesbir Singh Khela, from Letchworth, was found near Langford.
The men are being questioned after a 47-year-old man was found dead in a destroyed Skoda in February.
The 47-year-old was seen with his vehicle at a petrol station the day before he died, police say.
Linda Belgrove, 70, has helped raised almost £100,000 towards the welfare of retired police dogs.
The inquiry is into the death of Jesbir Singh Khela, from Letchworth, who was found in Bedfordshire.
Coins and pottery dating back more than 3,000 years are discovered.
Andy Knight says each year his two displays have got "bigger and bigger".
The company, which exports its product to more than 60 countries, will build a new site in Essex.
