THERE’S a dramatic development in the Mick Jagger-Jerry Hall divorce saga. I understand the distraught and angry Jerry has hired one of L.A.’s top law firms and its in-house private investigators.

The leggy, blond former supermodel has instructed the shamuses to comb through seven years of phone records from the couple’s mansion in the entertainment capital. The idea is to prove that Mick used the place as a love nest when he was on the West Coast recording and she was back in England raising their children.

It is one more sign Jerry is not going to meekly accept the fact that her divorce must be heard in Britain, where she has no chance of getting up to half of Jagger’s estimated $200 million fortune.

Her new lawyers think she can get the case moved to California and agree that additional proof of Mick’s serial philandering can’t do any harm.

Meanwhile, Jagger’s popularity is slumping at home. He is being trashed in the Fleet Street news-papers, with even the august Times of London cautioning Jerry that she’s going to have a terrible time squeezing blood from this Stone. It describes Mick as ”a rather pathetic old roue, desperately trying to recapture his long-vanished youth by pursuing girls as young as his two older daughters.”

The Times has gone right back to Mick’s marriage to Bianca Jagger to demonstrate how mean he is. When Mick and Bianca wed in St. Tropez in 1971, the paper reports, the look on Bianca’s face was mistaken for cool arrogance; in fact, she was distraught because, that very morning, Jagger had asked her to sign a document waiving all claims on his property in the event of their divorce. Prenups were unheard of in that place and time.

”My marriage ended on my wedding day,” Bianca later sadly remarked.

When they divorced, Mick managed to keep the case out of the American courts. A British judge awarded Bianca a measly $1 million or so.