Thinking it over... Russell Brand sends Katy Perry an email which says filing for divorce was the 'biggest mistake' of his life

By Fehintola Betiku

Seems like Russell Brand's dealing with a cold case of you don't know what you've got until it's gone.

The British comic is said to be 'seething with jealously' after his ex-wife Katy Perry was pictured at the Coachella Festival last month with Robert Ackroyd of Florence And The Machine.

Which led the actor to send her a long email admitting that he 'gave up' on their marriage too soon.

Full of regret: Russell Brand is said to be 'seething with jealously' at the thought of Katy Perry moving on

Brand filed for divorce from Perry in December and cited 'irreconcilable differences' as the reason for the split but now it appears being faced with the green-eyed monster has caused him to think things over.

It has been reported that Russell sent the 27-year-old singer an emotional e-mail in which he has asked for a second chance and said ending their 14 month marriage was a 'mistake'.

A source close to the 36-year-old told Grazia, 'Word has it Russell was "seething with jealousy" when he saw pictures of her with Rob. He apparently feels he gave up on their relationship too easily.'

I still love ya son: Brand enjoyed a leisurely lunch with his mother Barbara

The source continued, 'It's fair to say that Russell only wishes Katy happiness but perhaps he should have realised just how special his wife was when he was married to her rather than five months later.'

When Russell filed for divorce at the end of last year, it was reported that he did not agree with Katy's partying lifestyle and he told her to 'tone it down'.

Added to the fact that Katy was on a mammoth tour it seems their marriage ultimately paid the cost.

Although Katy has moved on, Russell was spotted with the main woman in his life - his beloved mother Barbara.

Moving on: Katy was pictured at Coachella in April cuddling up with Robert Ackroyd of Florence and the Machine

The comedian and his mum were spotted lunching in Primrose Hill, North London today.

Yesterday the California Gurls singer tweeted a line from Forrest Gump: 'Dear God make me a bird, so I can fly far far far away from here.'

Which could possibly be a sign that she might be thinking things over as well.