System: Favourite at 5/1 or bigger in a big handicap

Mechanism and rationale

In a handicap of fourteen or more the favourite is often 5/1 or longer. Being the one horse the whole market settled on is worth more than that price says: horses at the same price that are not favourite only match their odds. It loses at bookmaker starting price and pays at Betfair SP.

The rule

is_handicap = 1 AND is_favourite = 1 AND sp_decimal >= 6 AND field_size >= 14

Reads: is_handicap, is_favourite, sp_decimal, field_size

Pre-registration

Spec hash (sha256 of the canonical pre-spec)

not designed yet

Frozen

not frozen

The definition can still change.

Backing

exchange

Kind

system

Live from

2026-10-13

Matched

{
  "hypothesis_id": "H199-favourite-at-a-big-price-in-a-big-handicap",
  "similarity": 1,
  "variant": "broad"
}

Published

true

Rules

• The race is a handicap with 14 or more runners.
• Back the favourite when it starts at 5/1 or bigger. Joint favourites are all backed.

Source

Market analysis, October 2026

System id

big-price-favourite-big-handicap

Tier

none

Where

is_handicap = 1 AND is_favourite = 1 AND sp_decimal >= 6 AND field_size >= 14

Discovery result

Not measured yet.

Falsification

No attacks yet. Only promising ideas are attacked.

Sealed holdout (vault)

Not queried. Only a frozen idea can spend its one query against the 2020-25 holdout.

Forward record

No forward record. Shadow tracking starts after the vault and counts only races run after the freeze.

Lineage

Agent runs

• investigator v1ok · 1m 16s · 16 Oct, 15:52

  Output (schema-checked)

  {
    "reflection": "The thread keeps showing the same thing. Big-handicap favourites and second favourites at 5/1+ have beaten their price since October 2025: H199 scored 1.11 to 1.14, and second favourites 1.158 on 721. Third favourites did not (1.011 on 1,246), so whatever is going on stops at the top two in the betting. The 18+ runner sharpen (H-6da42014) pointed the right way at 1.224 on 293. It held on 6/6 neighbours and survived 6/6 attacks, but was killed on country: Ireland 0.951 against GB 1.57 on 122 bets. That is now the third pool where Ireland sits at par (0.99, 0.95) and GB carries all of the lift (1.40, 1.57). The pools overlap, so this is one pattern seen three times, not three confirmations. Two cautions on top of that. The second-favourite version shrank to 1.04 on 4,207 bets over the full vault history, so the October 2025+ window overstates this cluster. And the bigger-field sharpen did not show a bigger effect than the 14+ runner pool beyond what noise allows (p 0.12). What the chain has taught: field size is not where the effect lives, and neither, probably, is favourite status. The live question is whether a GB-only short-end effect survives the long history. There is no country column, but the `course` text column lets a GB-only rule be written by excluding the Irish course names. So the test that matters now is GB-only H199 against the vault. Slicing the 18+ near miss further would not tell us anything.",
    "answers": [
      {
        "question_id": "Q-9f80ceb9",
        "answer": "No country column exists (a catalogue search for 'country' returned nothing). But `course` (upper-case name) is pre-off from 2020, so a GB-only rule can be written today as course NOT IN a list of the 26 Irish track names. A proper flag would still be cleaner."
      }
    ],
    "questions": [
      {
        "question": "Is the GB/Ireland gap in big-handicap short-end runners a country effect, or a big-yard effect? Irish big handicaps are dominated by a few huge yards whose runners may be over-bet on reputation.",
        "rationale": "Ireland has been at par in every split (0.99, 0.95), GB well above. If the Irish par comes from mega-yard runners at the front of the market, then excluding big yards should bring Ireland up to GB's level and the rule would carry over. If Ireland stays at par without them, it is a market-structure difference between the countries. Columns: trainer_runs, trainer_id, course, sp_rank, sp_decimal, field_size, is_handicap.",
        "observation_ids": [
          "O-c4fd3752",
          "O-875c02ce",
          "O-d291de7f"
        ],
        "priority": 0.55
      },
      {
        "question": "Does the GB-only version of the live H199 rule hold up over the full history from 2020, or shrink towards par as the pooled second-favourite rival did (1.158 to 1.04)?",
        "rationale": "This decides whether SYS-big-price-favourite-big-handicap should be judged and staked on its GB bets only. Columns: course, is_favourite, sp_decimal, field_size, is_handicap, book_pct.",
        "observation_ids": [
          "O-c4fd3752",
          "O-875c02ce",
          "O-48574e29"
        ],
        "priority": 0.8
      }
    ],
    "hypotheses": [
      {
        "title": "Replicate: H199 favourites at 5/1+ in 14+ runner handicaps at GB courses only",
        "family": "race-betting",
        "operator": "replicate",
        "question_id": "Q-c7c25090",
        "new_question": null,
        "parent_id": "H199-favourite-at-a-big-price-in-a-big-handicap",
        "reasoning": {
          "observation_ids": [
            "O-c4fd3752",
            "O-875c02ce",
            "O-d291de7f",
            "O-48574e29"
          ],
          "question": "Is the live H199 lift carried by GB alone, and does it survive the full history once the Irish races at par are taken out?",
          "mechanism": "GB big-field handicaps are priced by a deep off-course book with generous each-way terms. Money spreads across the field, and the bookmakers put their margin on the front of the market less heavily than on the long tail. The horse the market settles on at 5/1+ ends up a little too long. Irish big handicaps form their prices differently (smaller ring, more informed stable money) and come out at par.",
          "market_miss": "SP at 5/1+ is set against same-priced horses that are fourth or fifth choice in smaller fields. Pooled GB+IRE figures hide the GB edge, so neither the market nor the form book singles it out.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.15 to 1.35 on 250+ discovery bets; 1.06+ on the vault",
            "falsified_if": "A/E 1.03 or below on the full-history vault, or GB-only discovery no higher than the pooled 1.11"
          },
          "rule_sketch": "is_handicap = 1 AND is_favourite = 1 AND sp_decimal >= 6 AND field_size >= 14 AND course NOT IN ('LEOPARDSTOWN','CURRAGH','THE CURRAGH','PUNCHESTOWN','FAIRYHOUSE','GALWAY','NAAS','GOWRAN PARK','DUNDALK','CORK','LIMERICK','NAVAN','LISTOWEL','TRAMORE','KILLARNEY','BALLINROBE','BELLEWSTOWN','CLONMEL','DOWN ROYAL','DOWNPATRICK','KILBEGGAN','LAYTOWN','ROSCOMMON','SLIGO','THURLES','TIPPERARY','WEXFORD')"
        },
        "confounders": [
          "the GB/IRE split was found after the fact in overlapping pools",
          "course name spellings may not match the list exactly",
          "GB festival handicaps (Cheltenham, Aintree) may carry the lift",
          "the edge may be at BSP only, not at SP"
        ],
        "expected_survival": 0.35
      },
      {
        "title": "Rival: Irish par is a big-yard effect, not a country effect",
        "family": "race-betting",
        "operator": "rival-explanation",
        "question_id": null,
        "new_question": 0,
        "parent_id": "H-6da42014",
        "reasoning": {
          "observation_ids": [
            "O-c4fd3752",
            "O-875c02ce",
            "O-d291de7f"
          ],
          "question": "Do top-two 5/1+ runners in big handicaps from smaller yards beat their price in both countries, so that Ireland's par comes from mega-yard runners being over-bet?",
          "mechanism": "In Irish big handicaps a few huge yards run several horses each, and their best-backed one draws money on the yard's name. That pushes its price below fair and cancels the front-of-market lift. Smaller yards' runners at the top of the market got there on the money alone, without that reputation push.",
          "market_miss": "Punters treat big-yard runners as the informed choice, and the yard's record makes them look stronger than the individual horse's handicap mark warrants.",
          "prediction": {
            "direction": "positive",
            "size": "A/E 1.08 to 1.18 on 500+ bets, with the IRE subset above 1.03",
            "falsified_if": "The IRE subset stays at 1.00 or below while GB stays high, which would point to country/market structure rather than yards"
          },
          "rule_sketch": "is_handicap = 1 AND sp_rank <= 2 AND sp_decimal >= 6 AND field_size >= 14 AND trainer_runs < 1500"
        },
        "confounders": [
          "trainer_runs is cumulative from 2020, so it grows over time and sorts yards differently in early and late periods",
          "the 1500 cut is a guess at what counts as a big yard",
          "yard size and country are correlated"
        ],
        "expected_survival": 0.25
      }
    ],
    "findings": [
      {
        "statement": "Restricting to 18+ runner handicaps raised the top-two-at-5/1+ figure to 1.224 on 293, but Ireland sat at 0.951 and the rule was killed. Bigger fields did not fix the Irish par, so field size is not the lever.",
        "kind": "fails",
        "observation_ids": [
          "O-c4fd3752",
          "O-875c02ce"
        ]
      },
      {
        "statement": "Every country split of the big-handicap short-end pools has shown the same pattern: GB 1.40 and 1.57 against Ireland 0.99 and 0.95. The pools overlap, so this is one pattern seen more than once, not independent replications.",
        "kind": "data",
        "observation_ids": [
          "O-875c02ce",
          "O-d291de7f",
          "O-c4fd3752"
        ]
      },
      {
        "statement": "A GB-only rule can be written with the pre-off `course` text column (excluding Irish track names), even though there is no country flag.",
        "kind": "method",
        "observation_ids": [
          "O-c4fd3752"
        ]
      }
    ]
  }

Timeline

1. hypothesis note SYS-big-price-favourite-big-handicap

   15 Oct, 23:10 · importer

2. New idea SYS-big-price-favourite-big-handicap: System: Favourite at 5/1 or bigger in a big handicap (import)

   15 Oct, 23:10 · importer

Every change is an event with an actor: an agent and its version, an engine, a human, or the importer. Current stage: Live.