A teacher is getting on his bike for a mammoth 254-mile ride in memory of his best friend who went to sleep and never woke up.

Aled Hopkin and his brother Gwilym will be raising funds for the Gareth Thomas Memorial Fund, set up by parents Ann and Trefor Thomas to help the work of charity Cardiac Risk in the Young (CRY). 

The charity raises awareness of Sudden Cardiac Death Syndrome, which claims the lives of 12 otherwise healthy people under the age of 35 in the UK every week. 

A law and international politics graduate, 21-year-old Gareth, from Llantrisant, died from an undiagnosed heart condition in February 2007 and his family and friends have since raised thousands of pounds for the memorial fund. 

The brothers, from Llanharry, will set off from Holyhead today and hope to arrive in Cardiff Bay on Sunday, averaging 50 miles a day on the Lon Las Cymru trail riding through breathtaking scenery across three mountain ranges. 

Aled and Gareth had been friends from the age of four.  After both graduated from Aberystwyth University they shared a house with two other old school friends in Roath, Cardiff. 

Now Aled, 24, and younger brother Gwilym, a sports science student, have decided they would like to fundraise every summer. 

"We know CRY gave a lot of support to Gareth's parents," said Aled. 

"Gareth's death was so sudden and such a shock, devastating.  We were all searching for answers and reasons. 

"As things started to sink in you started to realise that it has happened to quite a lot of people and that's why we want to raise the profile of the memorial fund and the work of CRY, as well as funds." 

For Anne and Trefor and their daughter Sian, 26, "life has changed forever." 

"When Gareth's heart stopped it broke all our hearts," said Anne.  "We have put our energy into the fund for CRY which gives us some sense of relief that we are doing something to help others and keeping Gareth's memory alive, that's very important to us." 

When news of Gareth's death was broken, because of a nursing background Anne said he felt pretty sure that it was from a heart condition.  She recalled how the day before her son was found dead, he and Aled had travelled up to Llanharry to watch rugby with Gwilym. 

Gareth had gone to bed around 2.30am.  At 3.30pm his friends had looked in on him and thought that he was still asleep and as he had had a late night they decided to leave him alone. 

When they returned to the house two hours later he was still in bed - and they made the tragic discovery.  They called an ambulance and tried to revive him, but there was nothing anyone could do. 

"We will never get over the horrors of that evening and can only imagine how it must have been for Gareth's friends," said Anne. 

"To go to bed and just never wake up again... it's very peaceful but it's too young to go. 

"He was just starting out on life.  He had done all the hard work and he was hoping to make a life for himself. 

"Our grief is forever, it just doesn't make sense. 

"It's very shocking to send someone off to bed and they never wake up and for his friends to find Gareth was desperately tragic for them." 

If you wish to donate or sponsor Aled and Gwilym Hopkin visit their Just Giving page justgiving.com/lonlascymuchallenge