Additional info. If I inserted a previously written disc, I can access the data on the disc, but on inserting the disc, the following
messages are generated:

Jul  7 21:53:53 Ubuntu-Bernard kernel: [  778.058900] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:53:53 Ubuntu-Bernard kernel: [  778.058912] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:53:53 Ubuntu-Bernard kernel: [  778.058920] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:53:53 Ubuntu-Bernard kernel: [  778.058938] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:53:56 Ubuntu-Bernard kernel: [  780.943327] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:53:56 Ubuntu-Bernard kernel: [  780.943340] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:53:56 Ubuntu-Bernard kernel: [  780.943348] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:53:56 Ubuntu-Bernard kernel: [  780.943366] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:53:58 Ubuntu-Bernard kernel: [  783.756717] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:53:58 Ubuntu-Bernard kernel: [  783.756729] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:53:58 Ubuntu-Bernard kernel: [  783.756738] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:53:58 Ubuntu-Bernard kernel: [  783.756755] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:54:01 Ubuntu-Bernard kernel: [  786.570495] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:54:01 Ubuntu-Bernard kernel: [  786.570507] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:54:01 Ubuntu-Bernard kernel: [  786.570516] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:54:01 Ubuntu-Bernard kernel: [  786.570533] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:54:04 Ubuntu-Bernard kernel: [  789.313557] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:54:04 Ubuntu-Bernard kernel: [  789.313569] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:54:04 Ubuntu-Bernard kernel: [  789.313578] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:54:04 Ubuntu-Bernard kernel: [  789.313595] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:54:07 Ubuntu-Bernard kernel: [  792.056316] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:54:07 Ubuntu-Bernard kernel: [  792.056329] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:54:07 Ubuntu-Bernard kernel: [  792.056338] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:54:07 Ubuntu-Bernard kernel: [  792.056357] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00
Jul  7 21:54:09 Ubuntu-Bernard kernel: [  794.799074] sr 1:0:1:0: [sr1] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
Jul  7 21:54:09 Ubuntu-Bernard kernel: [  794.799087] sr 1:0:1:0: [sr1] Sense Key : Illegal Request [current] 
Jul  7 21:54:09 Ubuntu-Bernard kernel: [  794.799095] sr 1:0:1:0: [sr1] Add. Sense: Illegal mode for this track
Jul  7 21:54:09 Ubuntu-Bernard kernel: [  794.799113] sr 1:0:1:0: [sr1] CDB: Read(10): 28 00 00 04 ac ba 00 00 02 00