Marriage brickwall

[Pinefamily]

I have a longstanding brick wall that hopefully some clever person(s) on here can help sort out.
Francis Bentham and his wife Margaret had several children baptized in Bedfordshire, where Francis was himself baptized in 1605. The first child was baptized in 1626 in Bedfordshire. I know Margaret's name from his will. The family ended up in London. To date I have been unable to find a marriage. Someone previously looked at Bedfordshire marriages on CD but found nothing.
I have checked both Ancestry and FMP to no avail.
Thanks in advance.