Is ignorance of the law sufficient to prevent a plaintiff from filing a late claim against a public entity?

"Mere ignorance of the law, at least where coupled with negligence in failing to look it up, is not sufficient cause to allow a petitioner to file a late claim against a public entity (Tammen v. County of San Diego, 66 Cal.2d 468, 476 [58 Cal.Rptr. 249, 426 P.2d 753]; Security Truck Line v. City of Monterey, 117 Cal.App.2d 441, 445 [256 P.2d 366, 257 P.2d 755] )." (Martin v. City of Madera (1968) 265 Cal.App.2d 76, 79, 70 Cal.Rptr. 908.)

Moreover, a petitioner may not successfully argue excusable neglect when he fails to take any action in pursuit of the claim within the 100-day period. "[T]he claimant must at a minimum make a diligent effort to obtain legal counsel within 100 days after the accrual of the cause of action.... The reasonable and prudent course of conduct under the circumstances of this case was to seek legal counsel." (Ebersol v. Cowan, supra, 35 Cal.3d at p. 439, 197 Cal.Rptr. 601, 673 P.2d 271.)