As of September 29, 2026, White Mountains Insurance's top three insider holders are Robert Lawrence Seelig (Evp General Counsel, 17.86K shares), George Manning Rountree (Chief Executive Officer, 13.81K shares), Reid Tarlton Campbell (President, 10.57K shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Robert Lawrence Seelig | Evp General Counsel | 20,357 | 0 | 20,357 | 23.4% | 20 Mar, 2026 |
| 2 | George Manning Rountree | Chief Executive Officer | 19,234 | 0 | 19,234 | 22.1% | 22 Dec, 2025 |
| 3 | Reid Tarlton Campbell | President | 10,575 | 0 | 10,575 | 12.1% | 21 May, 2026 |
| 4 | Liam P Caffrey | Chief Executive Officer | 8,705 | 0 | 8,705 | 10.0% | 25 Feb, 2026 |
| 5 | Morgan W Davis | President, American Centennial | 6,709 | 0 | 6,709 | 7.7% | 29 Dec, 2022 |
| 6 | Michaela Hildreth | Md Chief Accounting Officer | 4,316 | 0 | 4,316 | 5.0% | 25 Feb, 2026 |
| 7 | Weston M Hicks | Director | 2,936 | 0 | 2,936 | 3.4% | 21 May, 2026 |
| 8 | Giles E Harrison | President | 2,675 | 0 | 2,675 | 3.1% | 25 Feb, 2026 |
| 9 | David Allen Tanner | Director | 2,012 | 0 | 2,012 | 2.3% | 31 Aug, 2026 |
| 10 | Mary C Choksi | Director | 1,993 | 0 | 1,993 | 2.3% | 21 May, 2026 |
| 11 | Michael A Papamichael | Chief Financial Officer | 1,972 | 0 | 1,972 | 2.3% | 25 Feb, 2026 |
| 12 | Philip A Gelston | Director | 1,703 | 0 | 1,703 | 2.0% | 21 May, 2026 |
| 13 | Margaret Dillon | Director | 1,080 | 0 | 1,080 | 1.2% | 21 May, 2026 |
| 14 | Suzanne F. Shank | Director | 1,006 | 0 | 1,006 | 1.2% | 21 May, 2026 |
| 15 | Peter M Carlson | Director | 852 | 0 | 852 | 1.0% | 21 May, 2026 |
| 16 | Steven Yi | Director | 525 | 0 | 525 | 0.6% | 23 May, 2025 |
| 17 | John Chu | Director | 335 | 0 | 335 | 0.4% | 21 May, 2026 |
| 18 | Stephen Klar | Director | 113 | 0 | 113 | 0.1% | 27 Aug, 2026 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 31 Aug, 2026 | David Allen Tanner | Director | Disposed G | 2 | $0.00 | $0 | 2,012 | Direct |
| 26 Aug, 2026 | Stephen Klar | Director | Acquired A | 113 | $0.00 | $0 | 113 | Direct |
| 21 May, 2026 | David Allen Tanner | Director | Acquired A | 135 | $0.00 | $0 | 2,014 | Direct |
| 21 May, 2026 | Reid Tarlton Campbell | Director | Acquired A | 135 | $0.00 | $0 | 10,575 | Direct |
| 21 May, 2026 | Weston M Hicks | Director | Acquired A | 190 | $0.00 | $0 | 2,936 | Direct |
| 21 May, 2026 | Margaret Dillon | Director | Acquired A | 135 | $0.00 | $0 | 1,080 | Direct |
| 21 May, 2026 | Suzanne F. Shank | Director | Acquired A | 135 | $0.00 | $0 | 1,006 | Direct |
| 21 May, 2026 | Philip A Gelston | Director | Acquired A | 135 | $0.00 | $0 | 1,703 | Direct |
| 21 May, 2026 | Mary C Choksi | Director | Acquired A | 135 | $0.00 | $0 | 1,993 | Direct |
| 21 May, 2026 | John Chu | Director | Acquired A | 135 | $0.00 | $0 | 335 | Direct |
| 21 May, 2026 | Peter M Carlson | Director | Acquired A | 135 | $0.00 | $0 | 852 | Direct |
| 19 Mar, 2026 | Robert Lawrence Seelig | Evp General Counsel | Disposed G | 50 | $0.00 | $0 | 17,857 | Direct |
| 04 Mar, 2026 | David Allen Tanner | Director | Disposed G | 225 | $0.00 | $0 | 1,879 | Direct |
| 25 Feb, 2026 | Michaela Hildreth | Md Chief Accounting Officer | Acquired A | 600 | $0.00 | $0 | 1,825 | Direct |
| 25 Feb, 2026 | Robert Lawrence Seelig | Evp General Counsel | Acquired A | 775 | $0.00 | $0 | 2,500 | Direct |
| 25 Feb, 2026 | Michael A Papamichael | Chief Financial Officer | Acquired A | 500 | $0.00 | $0 | 1,200 | Direct |
| 25 Feb, 2026 | Giles E Harrison | President | Acquired A | 775 | $0.00 | $0 | 2,675 | Direct |
| 25 Feb, 2026 | Liam P Caffrey | Chief Executive Officer | Acquired A | 1,500 | $0.00 | $0 | 3,650 | Direct |
| 01 Jan, 2026 | Michaela Hildreth | Md Chief Accounting Officer | Disposed F | 274 | $2,078.03 | $569.38K | 2,491 | Direct |
| 01 Jan, 2026 | Robert Lawrence Seelig | Evp General Counsel | Disposed F | 398 | $2,078.03 | $827.06K | 17,907 | Direct |