On Tuesday, it will be seven years since she was murdered in her home, the Old Coach House, at Sandal Grange Farm on Walton Lane,by arsonists as she slept.
During the early hours of November 10, 2008 the killer poured white spirit was poured through her letter box and set alight.
Det Supt David Pervin, who is leading the investigation into her death, said someone still had information which could prove vital in solving the crime.
He said: “We may be seven years on from Lea’s murder, but the unsolved questions still remain for her family and for West Yorkshire Police.
“It is difficult to understand why someone would wish harm on such as respected, popular and vibrant woman, in what was an offence with no clear motive.
“In a 30 year career as a detective, this enquiry remains my only unsolved murder investigation, and clearly I want to find answers for her relatives.”
Mrs Brooke was an active member of the community and regularly attended Wakefield Golf Club in Sandal.
She devoted her time to helping others through the Inner Wheel Club of Wakefield, which she had been a member of for more than 50 years.
In the hunt for Mrs Brooke’s killer, a reconstruction was broadcast on BBC’s Crimewatch in 2011 but no new witnesses came forward.
Det Supt Pervin said: “Someone knows who started the fire at Lea’s house on the evening of Monday November 10 and I can only presume having that knowledge and not sharing it must weigh increasingly heavily on them as the years pass.
“Again, I would ask that person to come forwards and provide some answers and justice for a good family who deserve both.
“I would appeal to anyone who can help this family and catch those responsible to contact us.”
Anyone with any information should contact police calling 101 quoting Operation Pitkennedy.
Alternatively, contact Crimestoppers, anonymously, on 0800 555111.