Loss of power

Hi there,
My 2008 110 defender (51k miles) is loosing power soon after start up or after a few minutes driving when slowing or stopped. Power is lost as the revs just drop and using the accelerator has no effect. This lasts for about 1-2 minutes when she then goes back to normal, this is happening more often ( 5 times ) yesterday.

I went to a local mechanic ( not a dealer ) and he used his diagnostics (Auto com) to check it and detected no engine fault codes. He could only suggest a potential problem with the fuel pump but can't be sure until it fails.

Does anyone have any suggestions as to what this could be? And would a dealers diagnostics tell me anymore than his?

Thanks in advance.

Lack of fuel to the engine. Either the fuel pump is not pumping enough fuel or there is a blockage in the line and filters.
Replace/clean the filter and sedimentor first as these don't get replaced often enough and will give no engine fault codes.