 | | | | Av Time | | | Place | Races | 1st | 2nd | 3rd | Trophies | |
|---|
 O'Malley T | 25.6 | | | 80 | 2 | 0 | 0 | 0 | | |
| 1984 | | 26:18:20 | | Stack P G & O'Malley T | Leaside | 87 | | | | | | |
| 1985 | | 24:52:07 | | Stack P G & O'Malley T | Leaside & NCYC | 72 | | | | | | |
| O'Meara Michael | 18.0 | | | 2 | 4 | 3 | 0 | 1 | | |
| 1996 | | 18:50:35 | | Fanning B & O'Meara Michael | Independent | 3 | | | | 1 | | |
| 1999 | | 17:51:30 | | Morrissey Jim & O'Meara Michael | Dollymount Sea Scouts & 180 Waterford | 1 | | 1 | | | Civilian | |
| 2002 | | 16:54:16 | | Morrissey Jim & O'Meara Michael | Dollymount Sea Scouts & 180 Waterford | 1 | | 1 | | | Civilian | |
| 2003 | | 18:35:41 | | Morrissey Jim & O'Meara Michael | Dollymount Sea Scouts & 180 Waterford | 1 | | 1 | | | Civilian | |
| O'Neil M T | 35.6 | | | 126 | 1 | 0 | 0 | 0 | | |
| 1988 | | 35:35:30 | | Longworth S J & O'Neil M T | RMA Sandhurst | 126 | | | | | | |
| O'Neill B | 21.0 | | | 32 | 1 | 0 | 0 | 0 | | |
| 1982 | | 21:02:22 | | O'Neill B & Macdonald A M | Liverpool University | 32 | | | | | | |
| O'neill Joseph | 23.9 | | | 41 | 1 | 0 | 0 | 0 | | |
| 2017 | | 23:53:56 | | O'neill Joseph & Rynn Sean | RMKA | 41 | | | | | | |
| O'Smotherly P J | 21.5 | | | 11 | 1 | 0 | 0 | 0 | | |
| 1998 | | 21:28:10 | | O'Smotherly P J & Crowson D N | Royal Engineers | 11 | | | | | | |
| O'Sullivan A V | 22.7 | | | 31 | 1 | 0 | 0 | 0 | | |
| 1980 | | 22:42:16 | | Helps E J & O'Sullivan A V | Newham | 31 | | | | | | |
| O'Sullivan B B | 23.9 | | | 17 | 1 | 0 | 0 | 0 | | |
| 1967 | | 23:56:00 | | Smart G W & O'Sullivan B B | 9th Ind Para Sqn RE | 17 | | | | | | |
| O Hanrahan Feargal | 25.1 | | | 69 | 1 | 0 | 0 | 0 | | |
| 2015 | | 25:03:31 | | Irwin William & O Hanrahan Feargal | Wwkc Ireland | 69 | | | | | | |
| O Keeffe Eavan | 16.8 | | | 2 | 1 | 0 | 1 | 0 | | |
| 2023 | | 16:45:55 | | Horkan David & O Keeffe Eavan | International & Celbridge Paddlers | 2 | | | 1 | | European | |
| Oakley Robin | 22.4 | | | 40 | 1 | 0 | 0 | 0 | | |
| 2009 | C2 | 22:26:27 | | Oakley Robin & Collison Chris | Hemel Hempstead | 40 | | | | | | |
| Oaten J E | 37.9 | | | 152 | 1 | 0 | 0 | 0 | | |
| 1987 | | 37:52:19 | | Edwards S N & Oaten J E | Viking | 152 | | | | | | |
| Oates A J | 43.6 | | | 97 | 2 | 0 | 0 | 0 | | |
| 1983 | | 50:40:06 | | Oates A J & James D | 10th Wakefield Scouts | 73 | | | | | | |
| 1986 | | 36:33:10 | | Delany D M & Oates A J | Pangbourne Advent. Dolphin | 120 | | | | | | |
| Oconnell Elly | 19.8 | | | 19 | 1 | 0 | 0 | 0 | | |
| 2023 | | 19:46:39 | | Oconnell Elly & Herwanger Jorg | Richmond | 19 | | | | | | |
| Offer T D | 23.4 | | | 62 | 1 | 0 | 0 | 0 | | |
| 1993 | | 23:21:58 | | Gerrard M F & Offer T D | Thames Valley Police | 62 | | | | | | |
| Offiler D | 29.4 | | | 15 | 1 | 0 | 0 | 0 | | |
| 1964 | | 29:21:25 | | Offiler D & Niven F | RAF Oakington | 15 | | | | | | |
| Ogbum W D | 31.1 | | | 73 | 2 | 0 | 0 | 0 | | |
| 1981 | | 34:45:56 | | Ogbum W D & Edyvean N J | Independent | 65 | | | | | | |
| 1982 | | 27:25:59 | | Ogbum W D & Pocock DA | Independent | 80 | | | | | | |
| Ogeman Elin | 26.4 | | | 87 | 1 | 0 | 0 | 0 | | |
| 2014 | | 26:22:55 | | Lynch Maria & Ogeman Elin | Southampton | 87 | | | | | | |
| Okopski P | 36.3 | | | 123 | 1 | 0 | 0 | 0 | | |
| 1989 | | 36:20:05 | | Gilholm A J & Okopski P | HMS Osprey | 123 | | | | | | |
| Oldham Peter | 26.4 | | | 39 | 3 | 0 | 0 | 0 | | |
| 2002 | C2 | 30:05:24 | | Broad James & Oldham Peter | Independent | 71 | | | | | | |
| 2003 | C2 | 25:58:12 | | Broad James & Oldham Peter | Independent | 21 | | | | | Canadian | |
| 2004 | C2 | 23:16:07 | | Oldham Peter & Broad James | Independent | 25 | | | | | Canadian | |
| Olding T | 26.9 | | | 76 | 1 | 0 | 0 | 0 | | |
| 1982 | | 26:53:33 | | Scott P & Olding T | Exeter | 76 | | | | | | |
| Oliphant M R | 40.5 | | | 56 | 1 | 0 | 0 | 0 | | |
| 1967 | | 40:33:00 | | Oliphant M R & McKinley D B | Britannia College Dartmouth | 56 | | | | | | |
| Olive A | 22.8 | | | 18 | 1 | 0 | 0 | 0 | | |
| 1998 | | 22:47:00 | | Franks P & Olive A | University of Exeter | 18 | | | | | University | |
| Oliver G F | 28.2 | | | 26 | 1 | 0 | 0 | 0 | | |
| 1976 | | 28:12:55 | | Oliver G F & Self A J | 10 Para | 26 | | | | | Home Built | |
| Oliver Geoff | 28.0 | | | 81 | 1 | 0 | 0 | 0 | | |
| 2012 | C2 | 27:58:46 | | Oliver Geoff & Howard Jim | Sutton Bingham And District | 81 | | | | | | |
| Oliver George | 20.5 | | | 22 | 4 | 0 | 0 | 0 | | |
| 1982 | | 19:48:16 | | Oliver George & Nadal Kathleen | Nottingham | 17 | | | | | Mixed,Home Built | |
| 1986 | | 19:56:55 | | Enoch Dave & Oliver George | Nottingham | 13 | | | | | | |
| 1987 | C2 | 21:42:36 | | Oliver George & Young K W | Nottingham | 43 | | | | | Canadian | |
| 1990 | | 20:35:12 | | Oliver George & Enoch Dave | Nottingham | 16 | | | | | | |
| Oliver Jonathan | 25.1 | | | 66 | 2 | 0 | 0 | 0 | | |
| 2015 | | 24:48:33 | | Newman Alex & Oliver Jonathan | Acu - Southampton Otc | 65 | | | | | | |
| 2017 | | 25:30:32 | | Oliver Jonathan & Lea Edward | Independent | 66 | | | | | | |
| Oliver K | 23.6 | | | 53 | 1 | 0 | 0 | 0 | | |
| 1990 | | 23:37:16 | | Oliver K & Essex R W | Warren | 53 | | | | | | |
| Oliver K J | 35.0 | | | 68 | 1 | 0 | 0 | 0 | | |
| 1981 | | 34:58:13 | | Oliver K J & Pickering J | Mullard's and Old Edwardians R.C. | 68 | | | | | | |
| Oliver L | 22.6 | | | 13 | 1 | 0 | 0 | 0 | | |
| 1983 | | 22:39:47 | | Catchlove R A F & Oliver L | Gillingham | 13 | | | | | | |
| Oliver P A | 20.3 | | | 17 | 5 | 0 | 0 | 0 | | |
| 1978 | | 20:06:21 | | Oliver P A & Hemsell R E | Royal Engineers | 10 | | | | | | |
| 1979 | | 19:40:23 | | Collins K & Oliver P A | Royal Engineers | 14 | | | | | | |
| 1981 | | 20:12:11 | | Oliver P A & Jardine G | Royal Engineers | 8 | | | | | | |
| 1982 | | 20:47:40 | | Oliver P A & Perfect R W J | Royal Engineers | 29 | | | | | | |
| 1985 | | 20:47:53 | | Oliver P A & Egglestone G R | Royal Engineers | 22 | | | | | | |
| Oliver P G | 37.3 | | | 133 | 1 | 0 | 0 | 0 | | |
| 1988 | | 37:16:15 | | Oliver P G & Murray P L | Independent | 133 | | | | | | |
| Oliver R | 29.8 | | | 18 | 1 | 0 | 0 | 0 | | |
| 1964 | | 29:46:11 | | Davis M & Oliver R | RMA Sandhurst | 18 | | | | | | |
| Oloenshaw D | 43.9 | | | 11 | 1 | 0 | 0 | 0 | | |
| 1959 | | 43:54:00 | | Blackford G & Oloenshaw D | Worcester | 11 | | | | | | |
| Olsen D J | 36.1 | | | 17 | 1 | 0 | 0 | 0 | | |
| 1960 | | 36:06:50 | | Olsen D J & Cox J | RAF Hullavington | 17 | | | | | | |
| Olsen R | 21.2 | | | 35 | 1 | 0 | 0 | 0 | | |
| 1987 | | 21:13:39 | | Richardson David & Olsen R | Gillingham | 35 | | | | | | |
| Olver M J | 35.1 | | | 34 | 1 | 0 | 0 | 0 | | |
| 1969 | | 35:05:44 | | Olver M J & Breach M C | RMA Sandhurst | 34 | | | | | | |
| Oooley M T | 24.3 | | | 62 | 1 | 0 | 0 | 0 | | |
| 1992 | | 24:17:05 | | MacLeod Morna Lelsey & Oooley M T | West Cumbria | 62 | | | | | | |
| Oram D A | 22.8 | | | 54 | 1 | 0 | 0 | 0 | | |
| 1988 | | 22:45:55 | | Tyler K F & Oram D A | 8th Regiment RCT | 54 | | | | | | |
| Orenstein Simon | 28.0 | | | 77 | 1 | 0 | 0 | 0 | | |
| 2011 | C2 | 28:02:38 | | Edwards Roger A & Orenstein Simon | Chelmsford | 77 | | | | | | |
| Orman P | 34.5 | | | 28 | 1 | 0 | 0 | 0 | | |
| 1963 | | 34:28:32 | | Helsby C & Orman P | RAF Compton Bassett | 28 | | | | | | |
| Orpe I C | 36.2 | | | 107 | 1 | 0 | 0 | 0 | | |
| 1993 | | 36:14:30 | | Wilson T W & Orpe I C | Independent | 107 | | | | | | |