Historic information wanted about an UK Ferrari 365 GT4 2+2

Today I was approached by a Dutch fellow 365/400/412 enthusiast to assist him in finding additional history about his car. It's a 365 he bought 3 years back from Hermann Diehl in Munich. This person imported the car from the UK in 1990. The car had been in maintenance at Manfred Irber in Munich, unfortunately the company no longer exists so no further information could be obtained. The car hasn't been registered at the Ferrari Club UK either, so again dire straits. Therefore I'm reaching out to my readers who might be able to help further. The chassis number of this car is 17539. Please contact me if you have any further information about this car.