Beach Boys' Bruce Johnston was ''appalled'' when his former bandmate Brian Wilson started taking drugs.

The 75-year-old singer-and-songwriter - who was addicted to LSD - has often spoken about his regret of taking psychedelic drugs due to the impact it has had on his mental health, including experiencing auditory hallucinations [hearing voices].

And Bruce has revealed he in fact penned 'Disney Girls' from the 1971 album 'Surf's Up' about his despair at young people chasing highs and how upset he was when he found out his friend was caught up in the trippy hippie phase of the 60s.

Speaking exclusively to BANG Showbiz at an album playback and Q&A of their new LP, 'The Beach Boys With The Royal Philharmonic Orchestra', at the hip new cafe and bar, Spiritland - which is fitted around a world-class music system - in the trendy area of Kings Cross, London, on Wednesday (13.06.18), Bruce said: ''I was appalled and sad for Brian [taking drugs]. Here we are in the fall out.

''My message is subtle, but I get crazy thinking of kids ... I hated the legalisation of drugs and marijuana .

'''Ok, now you can just smoke as you drink alcohol and drive..'''

Asked if he ever tried to persuade him to give up his addiction, he replied: ''I couldn't stop it.''

Whilst Brian's cousin-and-bandmate, Mike Love, agreed that it was his decision to make, adding: ''People have choices in their adult life and they can choose what they want with their life; positive things, healthy things or spiritual things or excessive that leap to not good endings.''

Speaking in 2012, Brian - who hasn't performed with the Beach Boys since 2012 for their 50th anniversary and album - admitted: ''I've told a lot of people don't take psychedelic drugs. It's mentally dangerous to take. I regret having taken LSD. It's a bad drug.''

'The Beach Boys With The Royal Philharmonic Orchestra' is out now.