I have just called DVLA.
If the photo is not renewed and the driver gets pulled then it is only a fine of max £1,000 and is not endorseable (points) - the same applies to not changing an address.
It in no way has any bearing on the validity of the licence in respect of the legal right to drive a vehicle for which the driver is entitled to drive.
At age 70, a medical which is the same one for LGVs & PCVs must be passed to retain pre 97 D1 & C1 entitlements.
This can cost from about £50 upwards and is worth shopping around for.
Have a medical to prove you are physically fit to drive a D1 or C1 using Form D4
Download the 8 page D4 Medical Form
Using this Link Please print and take to your GP if you have the facilities at home or work.
Please contact your GP or visit
www.driversmedicals.com who can provide low-cost medical examinations.
THIS LINK will take you to a list of some cheap medical places around the UK.